Additional Questions - Chapter 4 - Transition and Inner Transition Elements - 12th Chemistry Guide Samacheer Kalvi Solutions
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Additional Questions
1 Mark Questions andAnswers
I. Choose the correct answer.
Question 1.
The elements whose atom has incomplete $d$ sub-shell are called
(a) s-block element
(b) Alkali metals
(c) transition elements
(d) Representative elements
Answer:
(c) transition elements
Question 2.
Which one of the following is the other name of d-block elements?
(a) Chalcogens
(b) Halogens
(c) Inner-transition elements
(d) Transition elements
Answer:
(d) Transition elements
Question 3.
Which metals play an important role in the development of human civilization?
(a) $\mathrm{Al}$ and $\mathrm{Mg}$
(b) $\mathrm{Na}$ and $\mathrm{K}$
(c) $\mathrm{Fe}$ and $\mathrm{Cu}$
(d) $\mathrm{Mn}$ and $\mathrm{Ni}$
Answer:
(c) $\mathrm{Fe}$ and $\mathrm{Cu}$
Question 4.
Which transition element is used in light bulb filaments?
(a) $\mathrm{Al}$
(b) $\mathrm{Ni}$
(c) W
(d) $\mathrm{Fe}$
Answer:
(c) W
Question 5.
Which metal is used in manufacturing artificial joints?
(a) Molybdenum
(6) Titanium
(c) Tungsten
(d) Iron
Answer:
(b) Titanium
Question 6.
Which transition metal is applied in the manufacturing of boiler plants?
(a) Iron
(b) Copper
(c) Aluminium
(d) Molybdenum
Answer:
(d) Molybdenum
Question 7.
Identify the transition metal present in Hemoglobin
(a) Cobalt
(b) Iron
(c) Manganese
(d) Copper
Answer:
(b) Iron
Question 8.
Which of the following transition metal is present in Vitamin $\mathrm{B}_{12}$ ?
(a) Cobalt
(b) Platinum
(c) Copper
(d) Iron
Answer:
(a) Cobalt
Question 9.
The metal cobalt is present in
(a) Vitamin-A
(b) Vitamin-B
(c) Vitamin-B 12
(d) Vitamin- $B_6$
Answer:
(c) Vitamin- $B_{12}$
Question 10.
Consider the following statements.
(i) Transition metals occupy group-3 to group-12 of the modem periodic table.
(ii) Representative elements occupy group-3 to group-12 of the modem periodic table.
(iii) Except group-11 elements of all transition metals are hard.
(iv) d-block elements are mostly non-metals.
Which of the above statements is/are incorrect?
(a) (ii) and (iv)
(b) (i) and (iii)
(c) (iii) only
(d) (i) only
Answer:
(a) (ii) and (iv)
Question 11.
Consider the following statements.
(i) d-block elements composed of $3 \mathrm{~d}$ series, Sc to $\mathrm{Zn}$ ( $4^{\text {th }}$ period).
(ii) $4 \mathrm{~d}$ series composed of $\mathrm{Y}$ to $\mathrm{Cd}$.
(iii) 5 d series composed of $\mathrm{La}, \mathrm{Hf}$ to Mercury.
(iv) d-block elements composed of $4 \mathrm{~d}$ series $\mathrm{Y}$ to $\mathrm{Cd}$.
Which of the above statements is/are incorrect
(a) (i) and (iv)
(b) (i), (ii) and (iii)
(c) (iii) and (iv)
(d) (iv) only
Ans.
(b) (i), (ii) and (iii)
Question 12 .
Which of the following is the correct electronic configuration of $\operatorname{Sc}(Z=21)$ ?
(a) $[\mathrm{Ar}] 3 \mathrm{~d}^3$
(b) $[\mathrm{Ar}] 3 \mathrm{~d}^{\prime} 4 \mathrm{~s}^2$
(c) $[\mathrm{Ar}] 3 \mathrm{~d}^2 4 \mathrm{~s}^1$
(d) $[\mathrm{Ar}] 4 \mathrm{~s}^2 4 \mathrm{p}^{\prime}$
Answer:
(b) $[\mathrm{Ar}] 3 \mathrm{~d}^{\prime} 4 \mathrm{~s}^2$
Question 13.
The correct electronic configuration of $\mathrm{Cr}$ is
(a) $[\mathrm{Ar}] 3 \mathrm{~d}^4 4 \mathrm{~s}^2$
(b) $[\mathrm{Ar}] 3 \mathrm{~d}^5$
(c) $[\mathrm{Ar}] 3 \mathrm{~d}^5 4 \mathrm{~s}^1$
(d) $[\mathrm{Ar}] 3 \mathrm{~d}^6$
Answer:
(c) $[\mathrm{Ar}] 3 \mathrm{~d}^5 4 \mathrm{~s}^1$
Question 14.
Which of the following is the correct electronic configuration of copper?
(a) $[\mathrm{Ar}] 3 \mathrm{~d}^5 4 \mathrm{~s}^1$
(b) $[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^1$
(c) $[\mathrm{Ar}] 3 \mathrm{~d}^9 4 \mathrm{~s}^2$
(d) $[\mathrm{Ar}] 3 \mathrm{~d}^8 4 \mathrm{~s}^2 4 \mathrm{p}^1$
Answer:
(b) $[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^1$
Question 15.
Which one of the following is the general electronic configuration of transition elements?
(a) [Noble gas $\mathrm{ns}^2 \mathrm{np}^6$
(b) [Noble gas] $(\mathrm{n}-2) \mathrm{f}^{1-14}(\mathrm{n}-1) \mathrm{d}^{1-10} \mathrm{~ns}^2$
(c) [Noble gas] $(\mathrm{n}-1) \mathrm{d}^{1-10}(\mathrm{n}-1) \mathrm{f}^{1-14} \mathrm{~ns}^2$
(d) [Noble gas $](\mathrm{n}-1) \mathrm{d}^{1-10} \mathrm{~ns}^2$
Answer:
(d) [Noble gas $](\mathrm{n}-1) \mathrm{d}^{1-10} \mathrm{~ns}^2$
Question 16.
Which of the following d-block elements has the highest electrical conductivity at room temperature?
(a) Copper
(b) Silver
(c) Aluminium
(d) Tungsten
Answer:
(b) Silver
Question 17.
Consider the following statements.
(i) The melting point decreases from Scandium to Vanadium in $3 \mathrm{~d}$ series.
(ii) In $3 \mathrm{~d}$ transition series, atomic radius decreases from $\mathrm{Sc}$ to $\mathrm{V}$ and upto copper atomic radius nearly remains the same.
(iii) As we move down in $3 \mathrm{~d}$ transition series, atomic radius increases.
Which of the above statements is/are incorrect?
(a) (i) only
(b) (ii) only
(c) (iii) only
(d) (i), (ii) and (iii)
Answer:
(a) (i) only
Question 18.
Which of the following transition element exhibit only +3 oxidation state?
(a) $\mathrm{Cu}$
(b) Sc
(c) $\mathrm{Mn}$
(d) $\mathrm{Cr}$
Answer:
(b) $\mathrm{Sc}$
Question 19.
Which one of the following transition element has maximum oxidation states?
(a) Manganese
(b) Copper
(c) Scandium
(d) Titanium
Answer:
(a) Manganese
Question 20.
Consider the following statements.
(i) In $3 \mathrm{~d}$ series, the middle element Mn has +2 to +7 oxidation states.
(ii) The oxidation state of $\mathrm{Ru}$ and $\mathrm{Os}$ is +8 .
(iii) Scandium has six different oxidation states.
Which of the above statements is/are not correct?
(a) (i) and (ii)
(b) (ii) only
(c) (i) only
(d) (iii) only
Answer:
(d) (iii) only
Question 21.
Which one of the following elements show high positive electrode potential?
(a) $\mathrm{Ti}^{+}$
(b) $\mathrm{Mn}^{2+}$
(c) $\mathrm{CO}^{2+}$
(d) $\mathrm{Cr}^{2+}$
Answer:
(c) $\mathrm{CO}^{2+}$
Question 22.
Which one of the following elements show high negative electrode potential?
(a) Copper
(b) Manganese
(c) Cobalt
(d) Zinc
Answer:
(d) Zinc
Question 23.
Which one of the following is diamagnetic in nature?
(a) $\mathrm{Ti}^{3+}$
(b) $\mathrm{Cu}^{2+}$
(c) $\mathrm{Zn}^{2+}$
(d) $\mathrm{V}^{3+}$
Answer:
(c) $\mathrm{Zn}^{2+}$
Question 24.
Which one of the following is paramagnetic in nature?
(a) $\mathrm{Sc}^{3+}$
(b) $\mathrm{Ti}^{4+}$
(c) $\mathrm{V}^{5+}$
(d) $\mathrm{Cu}^{2+}$
Answer:
(d) $\mathrm{Cu}^{2+}$
Question 25.
Which of the following pair has maximum number of unpaired electrons?
(a) $\mathrm{Mn}^{2+}, \mathrm{Fe}^{3+}$
(b) $\mathrm{CO}^{3+}, \mathrm{Fe}^{2+}$
(c) $\mathrm{Cr}^{3+}, \mathrm{Mn}^{4+}$
(d) $\mathrm{Ti}^{2+}, \mathrm{V}^{3+}$
Answer:
(a) $\mathrm{Mn}^{2+}, \mathrm{Fe}^{3+}$
Question 26.
Which of the following pair has $\mathrm{d}^{10}$ electrons?
(a) $\mathrm{Ti}^{3+}, \mathrm{V}^{4+}$
(b) $\mathrm{CO}^{3+}, \mathrm{Fe}^{2+}$
(c) $\mathrm{Cu}^{+}, \mathrm{Zn}^{2+}$
(d) $\mathrm{Mn}^{2+}, \mathrm{Fe}^{3+}$
Answer:
(c) $\mathrm{Cu}^{+}, \mathrm{Zn}^{2+}$
Question 27.
Which of the following is used as a catalyst in the manufacture of sulphuric acid form $\mathrm{SO}_3$.
(a) $\mathrm{V}_3 \mathrm{O}_5$
(b) $\mathrm{Rh}-\mathrm{Ir}$
(c) $\mathrm{Ni}$
(d) $\mathrm{Fe}$
Answer:
(a) $\mathrm{V}_5 \mathrm{O}_5$
Question 28.
Which one of the following is Zeigler - Natta catalyst?
(a) $\mathrm{CO}_2(\mathrm{CO})_8$
(b) $\mathrm{Rh} / \mathrm{Ir}$ complex
(c) $\mathrm{TiCl}_4+\mathrm{Al}\left(\mathrm{C}_2 \mathrm{H}_5\right)_3$
(d) $\mathrm{Fe} / \mathrm{Mo}$
Answer:
(c) $\mathrm{TiCl}_4+\mathrm{Al}\left(\mathrm{C}_2 \mathrm{H}_5\right)_3$
Question 29.
Which one of the following is used as a catalyst in the polymerisation of propylene?
(a) $\mathrm{V}_2 \mathrm{O}_5$
(b) $\mathrm{Pt}$
(c) $\mathrm{TiCl}_4+\mathrm{Al}\left(\mathrm{C}_2 \mathrm{H}_5\right)_3$
(d) $\mathrm{Fe} / \mathrm{Mo}$
Answer:
(c) $\mathrm{TiCl}_4+\mathrm{Al}\left(\mathrm{C}_2 \mathrm{H}_5\right)_3$
Question 30.
Consider the following statements.
(i) Transition metal hydrides are used as powerful oxidising agents.
(ii) Metallic carbides are chemically active.
(iii) Interstitial compounds are hard and show electrical and thermal conductivity.
Which of the above statements is/are incorrect?
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) only
(d) (i) only
Answer:
(a) (i) and (ii)
Question 31.
Which one of the following oxide is covalent?
(a) $\mathrm{Cr}_2 \mathrm{O}_3$
(b) $\mathrm{CrO}$
(c) $\mathrm{Mn}_2 \mathrm{O}_7$
(d) $\mathrm{Na}_2 \mathrm{O}$
Answer:
(c) $\mathrm{Mn}_2 \mathrm{O}_7$
Question 32.
Which one of the following oxide is amphoteric in nature?
(a) $\mathrm{CrO}$
(b) $\mathrm{Cr}_2 \mathrm{O}_3$
(c) $\mathrm{Mn}_2 \mathrm{O}_7$
(d) $\mathrm{MnO}$
Answer:
(b) $\mathrm{Cr}_2 \mathrm{O}_3$
Question 33.
The oxidation state of Chromium in $\mathrm{CrO}_4^{2-}$ and in $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$ are
(a) $+3,+6$
(b) $+7,+4$
(c) $+6,+6$
(d) $+4,+6$
Answer:
$(\mathrm{c})+6,+6$
Question 34.
Which one of the following is used to identify chloride ion in inorganic qualitative analysis?
(a) Barium chloride test
(b) Chromyl chloride test
(c) Brown ring test
(d) Ammonium molybdate test
Answer:
(b) Chromyl chloride test
Question 35.
Which one of the following is the formula of chromyl chloride?
(a) $\mathrm{CrOCl}_2$
(b) $\mathrm{CrCl}_3$
(c) $\mathrm{CrO}_2 \mathrm{Cl}_2$
(d) $\mathrm{CrCl}$
Answer:
(c) $\mathrm{CrO}_2 \mathrm{Cl}_2$
Question 36.
Which ore is used to prepare potassium permanganate?
(a) Pyrolusite
(b) Chromite
(c) Argentite
(d) Cuprite
Answer:
(a) Pyrolusite
Question 37.
Which one of the following geometry is possesed by permanganate ion?
(a) Pyramidal
(b) Tetrahedral
(c) Octahedral
(d) linear
Answer:
(b) Tetrahedral
Question 38 .
The hybridisation state of $\mathrm{Mn}^{+7}$ is permanganate ion is
(a) $\mathrm{sp}^2$ hybridisation
(b) $\mathrm{dsp}^2$ hybridisation
(c) $\mathrm{d}^2 \mathrm{sp}^3$ hybridisation
(d) $\mathrm{sp}^3$ hybridisation
Answer:
(d) $\mathrm{sp}^3$ hybridisation
Question 39.
Which one of the following is known as Baeyer's reagent?
(a) Cold dilute alkaline $\mathrm{KMnO}^4$
(b) Chromyl Chloride
(c) Acidified potassium dichromate
(d) Acidified potassium manganate
Answer:
(a) Cold dilute alkaline $\mathrm{KMnO}_4$
Question 40.
Which reagent is used in the conversion of ethylene into ethylene glycol?
(a) Chromyl chloride
(b) Zeigler - Natta catalyst
(c) Cold dilute alkaline $\mathrm{KMnO}_4$
(d) Acidified $\mathrm{K}_4 \mathrm{Cr}_2 \mathrm{O}_7$
Answer:
(c) Cold dilute alkaline $\mathrm{KMnO}_4$
Question 41.
Baeyer's reagent is used to detect unsaturation in an organic compound.
(a) Chloride ion
(b) unsaturated organic compound
(c) Sulphate ion
(d) Chromate ion
Answer:
(b) unsaturated organic compound
Question 42.
What is the equivalent weight of $\mathrm{KMnO}_4$ in acid medium?
(a) 158
(b) 52.67
(c) 31.6
(d) 392
Answer:
(c) 31.6
Question 43.
What is the equivalent weight of $\mathrm{KMnO}_4$ in basic medium?
(a) 158
(b) 52.67
(c) 392
(d) 31.6
Answer:
(a) 158
Question 44.
Which one of the following is used for the estimation of ferrous salts, oxalates, hydrogen peroxide and iodides?
(a) $\mathrm{K}_2 \mathrm{MnO}_4$
(ft) $\mathrm{KMnO}_4$
(c) $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$
(d) $\mathrm{CrO}_2 \mathrm{Cl}_2$
Answer:
(b) $\mathrm{KMnO}_4$
Question 45.
Which of the following is the general electronic configuration of lanthanoids?
(a) $[\mathrm{Xe}] 4 \mathrm{f}^7 3 \mathrm{~d}^{1-10} 5 \mathrm{~s}^2$
(b) $[\mathrm{Xe}] 4 \mathrm{f}^{1-14} 3 \mathrm{~d}^{10} 6 \mathrm{~s}^2$
(c) $[\mathrm{Xe}] 5 \mathrm{f}^{2-14} 4 \mathrm{~d}^{10} 6 \mathrm{~s}^2$
(d) $[\mathrm{Xe}] 4 \mathrm{f}^{2-14} 5 \mathrm{~d}^{1-10} 6 \mathrm{~s}^2$
Answer:
(d) $[\mathrm{Xe}] 4 \mathrm{f}^{2-14} 5 \mathrm{~d}^{1-10} 6 \mathrm{~s}^2$
Question 46.
The most common oxidation state of Lanthanoids is
(a) +4
(b) +3
(c) +6
(d) +5
Answer:
(b) +3
Question 47.
The expected electronic configuration of lanthanum ( $\mathrm{La})(\mathrm{Z}=57)$ is
(a) $[\mathrm{Xe}] 4 \mathrm{f}^1 5 \mathrm{~d}^{\circ} 6 \mathrm{~s}^2$
(b) $[\mathrm{Xe}] 4 \mathrm{f}^0 5 \mathrm{~d}^1 6 \mathrm{~s}^2$
(c) $[\mathrm{Xe}] 4 \mathrm{f}^3$
(d) $[\mathrm{Xe}] 4 \mathrm{f}^0 5 \mathrm{~d}^3$
Answer:
(a) $[\mathrm{Xe}] 4 \mathrm{f}^1 5 \mathrm{~d}^{\circ} 6 \mathrm{~s}^2$
Question 48.
The actual electronic configuration of $\mathrm{La}(\mathrm{Z}=57)$ is
(a) $[\mathrm{Xe}] 4 \mathrm{f}^1 5 \mathrm{~d}^{\circ} 6 \mathrm{~s}^2$
(b) $[\mathrm{Xe}] 4 \mathrm{f}^3$
(c) $[\mathrm{Xe}] 4 \mathrm{f}^0 5 \mathrm{~d}^1 6 \mathrm{~s}^2$
(d) $[\mathrm{Xe}] 4 \mathrm{f}^0 5 \mathrm{~d}^3$
Answer:
(c) $[\mathrm{Xe}] 4 \mathrm{f}^0 5 \mathrm{~d}^1 6 \mathrm{~s}^2$
Question 49.
Which of the following lanthanoids have half-filled $4 \mathrm{f}$ orbital?
(a) $\mathrm{Gd}$
(b) $\mathrm{Tb}$
(c) $\mathrm{Lu}$
(d) $\mathrm{La}$
Answer:
(a) $\mathrm{Gd}$
Question 50.
Which one of the following lanthanoids have completely filled $4 f$ orbital?
(a) $\mathrm{Gd}$ and $\mathrm{Eu}$
(b) $\mathrm{La}$ and $\mathrm{Ce}$
(c) $\mathrm{Yb}$ and $\mathrm{Lu}$
(d) $\operatorname{Pr}$ and $\mathrm{Pm}$
Answer:
(c) $\mathrm{Yb}$ and $\mathrm{Lu}$
Question 51.
Which one of the following is the main cause of lanthanoid contraction?
(a) Poor shielding effect of $5 \mathrm{f}$ sub-shell
(b) More shielding effect of $4 \mathrm{f}$ sub-shell
(c) Poor shielding effect of $4 \mathrm{f}$ sub-shell
(d) More shielding effect of $5 \mathrm{f}$ sub-shell
Answer:
(c) Poor shielding effect of $4 \mathrm{f}$ sub-shell
Question 52.
Which of the following pair has more or less same atomic radius due to lanthanide contraction?
(a) Ti and $\mathrm{V}$
(b) Fm and Md
(c) No and $\mathrm{Lr}$
(d) $\mathrm{Zr}$ and $\mathrm{Hf}$
Answer:
(d) $\mathrm{Zr}$ and $\mathrm{Hf}$
Question 53.
Consider the following statement.
(i) All the actinoids are non radioactive.
(ii) Neptunium and other heavier elements are produced by artificial transformation of naturally occurring elements by nuclear reactions.
(iii) Most of the actinoids have long half lives.
Which of the above statements is/are not correct.
(a) (i) only
(b) (i) and (ii)
(c) (ii) and (iii)
(d) (i) and (iii)
Answer:
(d) (i) and (iii)
Question 54.
The general valence shell electronic configuration of actinoids is
(a) $[\mathrm{Xe}] 4 \mathrm{f}^{2-14} 5 \mathrm{~d}^{0-2} 6 \mathrm{~s}^2$
(b) $[\mathrm{Rn}] 4 \mathrm{f}^{2-14} 5 \mathrm{~d}^{0-2} 6 \mathrm{~s}^2$
(c) $[\mathrm{Rn}] 5 \mathrm{f}^{2-14} 6 \mathrm{~d}^{0-1} 7 \mathrm{~s}^2$
(d) $[\mathrm{Rn}] 4 \mathrm{f}^{0-7} 5 \mathrm{~d}^{0-1} \mathrm{~s}^2$
Answer:
(c) $[\mathrm{Rn}] 5 \mathrm{f}^{2-14} 6 \mathrm{~d}^{0-2} 7 \mathrm{~s}^2$
Question 55.
Which pair of actinoids show +2 oxidation state?
(a) Am and Th
(b) $\mathrm{Pa}$ and $\mathrm{U}$
(c) $\mathrm{Pu}$ and $\mathrm{Cm}$
(d) No and $\mathrm{Lr}$
Answer:
(a) Am and Th
Question 56.
Neptunium and Plutonium exhibit the maximum oxidation state as
(a) +8
(b) +7
(c) +6
(d) +4
Answer:
(b) +7
Question 57.
Consider the following statement.
Answer:
(i) Most of the actinoids are coloured.
(ii) Actinoids show greater tendency to form complexes.
(iii) Most of the actinoids are non-radioactive.
Which of the above statements is/are correct.
(a) (i) only
(b) (i) and (iii)
(c) (i) and (ii)
(d) (ii) and (iii)
Answer:
(c) (i) and (ii)
Question 58.
Consider the following statement.
Answer:
(i) Lanthanoids do not form oxo cations.
(ii) Most of the lanthanoids are colourless.
(iii) Binding energy of $4 \mathrm{f}$ orbitals are lower.
Which of the above statement is/are not correct.
(a) (i) and (ii)
(b) (iii) only
(c) (i) and (iii)
(d) (i), (ii) and (iii)
Answer:
(b) (iii) only
Question 59.
Which one of the following is more basic in nature?
(a) $\mathrm{La}(\mathrm{OH})_3$
(b) $\mathrm{Ce}(\mathrm{OH})_3$
(c) $\mathrm{Gd}(\mathrm{OH})_3$
(d) $\mathrm{Lu}(\mathrm{OH})_3$
Answer:
(a) $\mathrm{La}(\mathrm{OH})_3$
Question 60 .
Which one of the following is less basic in nature?
Answer:
(a) $\mathrm{La}(\mathrm{OH})_3$
(b) $\mathrm{Gd}(\mathrm{OH})_3$
(c) $\mathrm{Lu}(\mathrm{OH})_3$
(d) $\mathrm{Ce}(\mathrm{OH})_3$
Answer:
(c) $\mathrm{LU}(\mathrm{OH})_3$
II. Fill in the blanks.
1. Transition elements occupy the central position of the periodic table between ........... elements.
2. Except ........... elements, all transition metals are hard and have very high melting point.
3. The metal present in Vitamin $-B_{12}$ is ...........
4.......... metal is used in manufacture of artificial joints.
5. The extra stability of $\mathrm{Cr}$ and $\mathrm{Cu}$ is due to ........... of electrons and exchange energy.
6. Of all the known elements ............ has the highest electrical conductivity at room temperature.
7. The maximum melting point at about the middle of transition metal series indicates that ................... configuration is favourable for strong attraction.
8. The atomic radius of $5 \mathrm{~d}$ elements and $4 \mathrm{~d}$ elements are nearly same due to ............
9. Ni (II) compounds are thermodynamically ...................... than Pt (II) compounds.
10. The first transition metal ..................... exhibits only +3 oxidation state.
11. The middle transition element ..................... has six different oxidation states.
12. The oxidation state of $\mathrm{Ru}$ and $\mathrm{Os}$ is ........................
$13 . \ldots \ldots \ldots \ldots$ is unique in $3 \mathrm{~d}$ series having a stable +1 oxidation state.
14. The substance which is oxidised is a ....................... agent and the one which is reduced is an agent.
15. The oxidising and reducing power of an element is measured in terms of ................
16. If the $\mathrm{E}^{\circ}$ of a metal is large and negative, the metal is a ...........
17. The species with all paired electrons exhibit ................
18. The magnetic moment of an ion is given by ..................
19. Many industrial processes use .......... or their as catalyst.
20. In the catalytic hydrogenation of an alkene ........... is used as catalyst.
21. In the preparation of acetic acid from acetaldehyde the catalyst used in ....................
22. The catalyst used in the hydroformylation of olefins is ............
23........... catalyst is used in polymerization of propylene.
24. Metallic carbides are chemically ...........
25. Except Scandium all other 3d series transition elements form .................. metal oxides.
26. $\mathrm{Cr}_2 \mathrm{O}_3 \ldots \ldots \ldots$............ is and $\mathrm{CrO}$ is in nature.
27. $\mathrm{Mn}_2 \mathrm{O}_7$ dissolves in water to give ..................
28. On heating potassium dichromate, it decomposes to give ..................... and molecular oxygen.
29. Potassium dichromate is a powerful ............... agent in acidic medium.
30 ............ is used in leather tanneries for chrome tanning.
31. Potassium dichromate is used in quantitative analysis for the estimation of ............. and .................
32. Permanganate ion has ........... geometry in which $\mathrm{Mn}^{+7}$ is hybridised.
33. Cold dilute alkaline $\mathrm{KMnO}_4$ is known as ...........
34. .......... is used for the treatment of skin infections and fungal infections of the foot.
35. Baeyer's reagent is used for detecting ........... in an organic compounds.
36. The equivalent weight of $\mathrm{KMnO}_4$ in neutral medium is ....................
37. The common oxidation state of lanthanoids is ...............
38. Due to the decrease in the size of $\mathrm{Ln}^{3+}$ ions, the ionic character of $\mathrm{Ln}-\mathrm{OH}$ bond decreases which results in the ..............
39. All the actinoids are. ..................... and most of them have .................... half lives.
40. ................... do not form oxo cations.
Answer:
1. sandpblock
2. group-II
3. cobalt
4. Titanium
5. symmetrical distribution
6. silver
7. $\mathrm{d}^5$, inter atomic
8. lanthanoid contraction
9. more stable
10. Scandium
11. Manganese
12. +8
13. Copper
14. reducing, oxidising
15. Standard electrode potential
16. powerful reducing agent
17. diamagnetism
18. $\mu=g \sqrt{S(S+1)} \mu_{\mathrm{B}}$
19. transition metals, compounds
20. Nickel
21. $\mathrm{Rh} / \mathrm{Ir}$ complex
22. $\mathrm{CO}_2(\mathrm{CO})_8$
23. Zeigler $-\mathrm{Natta}$ (or) $\mathrm{TiCl}_4+\mathrm{Al}\left(\mathrm{C}_2 \mathrm{H}_5\right)_3$
24. inert
25. ionic
26. amphoteric, basic
27. permanganic acid $\left(\mathrm{HMnO}_4\right)$
28. Chromium (III) oxide $-\mathrm{Cr}_2 \mathrm{O}_3$
29. Potassium dichrom.ate
30. iron compounds, iodides
31. tetrahedral,sp ${ }^3$
32. Baeyer's reagent
33. Potassium permanganate
34. unsaturation
35. 52.67
36. +3
37. decrease in the basicity
38. radioactive. shoit
39. Lanthanoids
III. Match the following using the code given below.
Question 1.
A. Tungsten -1 . Development of human civilization
B. Titanium -2 . Light bulb filament
C. Molybdenum -3 . Artificial joint
D. Copper -4 . Boiler plants
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Answer:
(a) $2,3,4,1$
Question 2.
A. Iron - 1. Artificial joints
B. Platinum - 2. Hemoglobin
C. Cobalt -3 . Catalysis
D. Titanium -4 . Vitamin $-B_{12}$
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Answer:
(b) $2,3,4,1$
Question 3.
A. Sc to $\mathrm{Zn}-1.5 \mathrm{~d}$ series
B. $\mathrm{Y}$ to $\mathrm{Cd}-2$. Actinoids
C. LatoHg - 3. 3dseries
D. Ac to $\mathrm{Lr}-4.4$ d series
.png)
Answer:
(a) $3,4,1,2$
Question 4.
A. $\mathrm{Cr}-1$. [Ar] $3 \mathrm{~d}^{10} 4 \mathrm{~s}^2$
B. $\mathrm{Cu}-2 .[\mathrm{Ar}] 3 \mathrm{~d}^5 4 \mathrm{~s}^1$
C. $\mathrm{Zn}-3 \cdot[\mathrm{Ar}] 3 \mathrm{~d}^1 4 \mathrm{~s}^2$
D. $\mathrm{Sc}-4 \cdot[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^1$
.png)
Answer:
(c) $2,4,1,3$
Question 5.
A. Scandium $-1 .+7$
B. Manganese $-2 .+2$
C. Copper $-3 .+3$
D. Titanium $-4 .+\mathrm{I}$
.png)
Answer:
(a) $3,1,4,2$
Question 6.
A. $\mathrm{Sc}^{3+}-1.3 \mathrm{~d}^1$
B. $\mathrm{Ti}^3-2.3 \mathrm{~d}^0$
C. $\mathrm{Mn}^{2+}-3.3 \mathrm{~d}^{10}$
D. $\mathrm{Zn}^{2+}-4 \cdot 3 \mathrm{~d}^5$
.png)
Answer:
(b) $2,1,4,3$
IV. Assertion and Reason.
Question 1.
Assertion (A) - Cr and Cu having $[\mathrm{Ar}] 3 \mathrm{~d}^5 4 \mathrm{~s}^1$ and $[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^1$ are more stable.
Reason (R) - The extra stability of elements $\mathrm{Cr}$ and $\mathrm{Cu}$ is due to symmetrical distribution of electrons and exchange energy.
(a) Both (A) and (R) are correct and (R) explains (A).
(b) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
(c) $(\mathrm{A})$ is correct but (R) is wrong.
(d) (A) is wrong but (R) is correct.
Answer:
(a) Both (A) and (R) are correct and (R) explains (A).
Question 2.
Assertion (A) - In $3 \mathrm{~d}$ transition elements, the expected decrease in atomic radius is observed from Sc to V, thereafter upto $\mathrm{Cu}$, the atomic radius nearly remains the same.
Reason (R) - As we move from Sc to V, the added $3 \mathrm{~d}$ electrons only partially shield the increased nuclear charge but upto $\mathrm{Cu}$, the extra electron added to $3 \mathrm{~d}$ sub-shell repel the $4 \mathrm{~s}$ electrons and the slight increase in nuclear charge operated in opposite direction and it leads to constancy in atomic radii.
(a) Both (A) and (R) are correct and (R) explains (A).
(b) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
(c) (A) is correct but (R) is wrong.
(d) (A) is wrong but (R) is correct.
Answer:
(a) Both (A) and (R) are correct and (R) explains (A).
Question 3.
Assertion (A) - In transition metal series, the ionization enthalpy increases.
Reason (R) - This is due to increase in nuclear charge corresponding to the filling of $d$ electrons.
(a) Both (A) and (R) are correct and (R) explains (A).
(b) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
(c) (A) is correct but (R) is wrong.
(d) (A) is wrong but (R) is correct.
Answer:
(a) Both (A) and (R) are correct and (R) explains (A).
Question 4.
Assertion (A) - Ni (II) compounds are thermodynamically more stable than Pt (II) compounds.
Reason (R) - The energy required to form $\mathrm{Ni}^{2-}$ is less than that of $\mathrm{Pt}^{2+}$.
(a) Both (A) and (R) are correct and (R) explains (A).
(b) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
(c) (A) is correct but (R) is wrong.
(d) (A) is wrong but (R) is correct.
Answer:
(a) Both (A) and (R) are correct and (R) explains (A).
Question 5.
Assertion (A) - Except Scandium all $3 \mathrm{~d}$ series, transition elements exhibit variable oxidation states. Reason $(\mathrm{R})$ - By loosing electrons from $(\mathrm{n}-1) \mathrm{d}$ orbital and ns orbital as the energy difference between them is very small.
(a) Both (A) and (R) are correct and (R) explains (A).
(b) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
(c) (A) is correct but (R) is wrong.
(d) $(\mathrm{A})$ is wrong but (R) is correct.
Answer:
(a) Both (A) and (R) are correct and (R) explains (A).
Question 6.
Assertion (A) $-\mathrm{Mn}^{2+}$ is more stable than $\mathrm{Mn}^{4+}$.
Reason $(\mathrm{R})-\mathrm{Mn}^{2+}\left(3 \mathrm{~d}^5\right)$ is more stable than $\mathrm{Mn}^{4+}\left(3 \mathrm{~d}^3\right)$ is due to extra stability of half-filled electronic configuration.
(a) Both (A) and (R) are correct and (R) is the correct explanation of (A)
(b) Both (A) and (R) are correct but (R) is not the correct explanation of (A)
(c) (A) is correct but (R) is wrong
(d) (A) is wrong but (R) is correct
Answer:
(a) Both (A) and (R) are correct and (R) is the correct explanation of (A)
Question 7.
Assertion (A) - Copper is unique in $3 \mathrm{~d}$ series having a stable +1 oxidation state.
Reason (R) - Copper is prone to disproportionate to the +2 and 0 oxidation states.
(a) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
(b) Both (A) and (R) are correct and (R) explains (A).
(c) (A) is correct but (R) is wrong.
(d) (A) is wrong but (R) is correct.
Answer:
(b) Both (A) and (R) are correct and (R) explains (A).
Answer:
(a) $\mathrm{CO}^{3+}$
Reason: It has positive reduction potential whereas others have negative reduction potential.
Question 9.
(a) $\mathrm{Mn}^{3+}$
(b) $\mathrm{Fe}^{3+}$
(c) $\mathrm{Cr}^{3+}$
(d) $\mathrm{CO}^{3+}$
Answer:
(c) $\mathrm{Cr}^{3+}$
Reason: It has negative reduction potential whereas others have positive reduction potential.
Question 10.
(a) $\mathrm{SC}^{3+}$
(b) $\mathrm{Ti}^{4+}$
(c) $\mathrm{V}^{5+}$
(d) $\mathrm{Cu}^{2+}$
Answer:
(d) $\mathrm{Cu}^{2+}$
Reason: It is paramagnetic whereas others are diamagnetic.
Question 11.
(a) $\mathrm{Cr}^{3+}$
(b) $\mathrm{Mn}^{4+}$
(c) $\mathrm{V}^{2+}$
(d) $\mathrm{Zn}^{2+}$
Answer:
(d) $\mathrm{Zn}^{2+}$
Reason: It is diamagnetic whereas others are paramagnetic
VI. Find Out the correct pair.
Question 1.
(a) $\mathrm{CrO}_4^{-}$and $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$
(b) $\mathrm{MnO}_4^{-}$and $\mathrm{MnO}_4^{2-}$
(c) $\mathrm{H}_2 \mathrm{CrO}_4$ and $\mathrm{HMnO}_4$
(d) $\mathrm{Cr}_2 \mathrm{O}_3$ and $\mathrm{Mn}_2 \mathrm{O}_7$
Answer:
(a) $\mathrm{CrO}_4^{-}$and $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$
In this pair $\mathrm{Cr}$ has +6 oxidation states whereas in others the metal has different oxidation state.
Question 2.
(a) $\mathrm{Zn}, \mathrm{Cu}$
(b) $\mathrm{Hf}, \mathrm{Zr}$
(c) $\mathrm{Ag}, \mathrm{Au}$
(d) $\mathrm{Ti}, \mathrm{Cu}$
Answer:
(b) $\mathrm{Hf}, \mathrm{Zr}$
This pair has same atomic radius whereas others have different atomic radius.
Question 3.
(a) $\mathrm{Ru}, \mathrm{Os}$
(b) $\mathrm{Mn}, \mathrm{Cu}$
(c) $\mathrm{Sc}, \mathrm{Cu}$
(d) $\mathrm{Ni}, \mathrm{Co}$
Answer:
(a) $\mathrm{Ru}, \mathrm{Os}$
Both has +8 as oxidation state whereas others have different oxidation state.
Question 4.
(a) $\mathrm{Ti}^{2+}, \mathrm{CO}^{2+}$
(b) $\mathrm{Cr}^{2+}, \mathrm{Mn}^{3+}$
(c) $\mathrm{Fe}^{2+}$ and $\mathrm{CO}^{3+}$
(d) $\mathrm{CO}^{3+}$ and $\mathrm{Cu}^{2+}$
Answer:
(d) $\mathrm{CO}^{3+}$ and $\mathrm{Cu}^{2+}$
Both have positive electrode potential whereas others have different value.
Question 5.
(a) $\mathrm{Cu}^{2+}, \mathrm{Zn}^{2+}$
(b) $\mathrm{CO}^{3+}, \mathrm{Cr}^{3+}$
(c) $\mathrm{Ti}^{3+}, \mathrm{V}^{3+}$
(d) $\mathrm{Mn}^{3+}, \mathrm{Cr}^{3+}$
Answer:
(c) $\mathrm{Ti}^{3+}, \mathrm{V}^{3+}$
have negative electrode potential whereas others have different values.
VII. Find out the incorrect pair.
Question 1.
(a) $\mathrm{Sc}^{3+}, \mathrm{Ti}^{4+}$
(b) $\mathrm{Ti}^{3+}, \mathrm{Ti}^{2+}$
(c) $\mathrm{Cr}^{2+}, \mathrm{Mn}^{3+}$
(d) $\mathrm{Cu}^{+}, \mathrm{Zn}^{2+}$
Answer:
(b) $\mathrm{Ti}^{3+}, \mathrm{Ti}^{2+}$
have $\mathrm{d}^1$ and $\mathrm{d}^1$ configuration whereas others have same configuration.
Question 2.
(a) $\mathrm{Sc}$ and $\mathrm{Zn}$
(b) $\mathrm{Y}$ and $\mathrm{Cd}$
(c) $\mathrm{Ag}$ and $\mathrm{Au}$
(d) $\mathrm{Na}$ and $\mathrm{K}$
Answer:
(d) Na and $\mathrm{K}$. They belong to alkaline metals whereas others are d-block elements.
2 Mark Questions and Answers
Question 1.
d-block elements are called transition elements. Justify this statement.
Answer:
1. d-block elements occupy the central position of the periodic table, between s and p block elements.
2. Their properties are transitional between highly reactive metals of s-block and elements of p-block which are mostly non-metals. That is why d-block elements are called transitional elements.
Question 2.
How many series are in d-bloclc elements? What are they?
Answer:
- There are 4 series in d-block elements They are,
- $3 \mathrm{~d}$ series - 4th period - Scandium to Zinc
- $4 \mathrm{~d}$ series - 5 th period - Yttrium to Cadmium
- $5 \mathrm{~d}$ series - 6th period - Lanthanum to Mercury
- $6 \mathrm{~d}$ series -7 th period - Actinium to Californium
Question 3.
$\mathrm{Zn}, \mathrm{Cd}, \mathrm{Hg}$ belong to d-block elements even though they do not have partially filled d-orbitals. Give reason.
Answer:
1. $\mathrm{Zn}, \mathrm{Cd}, \mathrm{Hg}$ belong to d-block elements even though they do not have partially filled d-orbitals either in their elemental state or in their normal oxidation states.
2. However they are treated as transition elements, because their properties are an extension of the properties of the respective transition elements.
Question 4.
Applying Aufbau principle, write down the electronic configuration of $\mathrm{Sc}(\mathrm{Z}=21)$ and $\mathrm{Zn}(\mathrm{Z}=30)$. Answer:
1. According to Aufbau principle, the electron first fills the $4 \mathrm{~s}$ orbital before $3 \mathrm{~d}$ orbital.
2. $\mathrm{Sc}(\mathrm{Z}=21) \mathrm{Is}^2 2 \mathrm{~s}^2 2 \mathrm{p}^6 3 \mathrm{~s}^2 3 \mathrm{p}^6 4 \mathrm{~s}^2 3 \mathrm{~d}^1$
- $\mathrm{Zn}(\mathrm{Z}=30) \mathrm{Is}^2 2 \mathrm{~s}^2 2 \mathrm{p}^6 3 \mathrm{~s}^2 3 \mathrm{p}^6 4 \mathrm{~s}^2 3 \mathrm{~d}^{10}$
Question 5.
Write a note about atomic radius of Zinc.
Answer:
At the end of $3 \mathrm{~d}$ series, $\mathrm{d}$-orbitals of Zinc contain 10 electrons in which the repulsive interaction between the electrons is more than the effective nuclear charge and hence the orbitals slightly expand and atomic radius slightly increases.
Question 6.
Write a not about oxidation state of $3 \mathrm{~d}$ series.
Answer:
1. The number of oxidation states increases with the number of electrons available, and it decreases as the number of paired electrons increases.
2. Hence, the first and last elements show less number of oxidation states and the middle elements with more number of oxidation states.
3. For example, the first element Sc has only one oxidation state +3 , the middle element Mn has six different oxidation states from +2 to +7 . The last element $\mathrm{Cu}$ shows +1 and +2 oxidation states only.
Question 7.
$\mathrm{Mn}^{2+}$ is more stable than $\mathrm{Mn}^{4+}$. Why?
Answer:
1. The relative stability of different oxidation states of $3 \mathrm{~d}$ metals is correlated with the extra stability of half-filled and fully filled electronic configurations.
2. Example $-\mathrm{Mn}^{2+}\left(3 \mathrm{~d}^5\right)$ is more stable than $\mathrm{Mn}^{4+}\left(3 \mathrm{~d}^3\right)$
Question 8.
$\mathrm{Ru}$ and Os have highest oxidation state in which compounds? Explain with example.
Answer:
1. $\mathrm{Ru}$ and Os have +8 as the highest oxidation state.
2. The highest oxidation state of $4 \mathrm{~d}$ and $5 \mathrm{~d}$ elements are found in their compounds with the higher electronegative elements like $\mathrm{O}, \mathrm{F}$ and $\mathrm{Cl}$. For example: $\mathrm{RuO}_4, \mathrm{OsO}_4$
Question 9.
Copper is unique in $3 \mathrm{~d}$ series. Prove this statement.
Answer:
Copper is unique in $3 \mathrm{~d}$ series having a stable +1 oxidation state. It is prone to disproportionate to the +2 and 0 oxidation states.
Question 10.
Define - Standard electrode potential.
Answer:
Standard electrode potential is the value of the standard emf of a cell in which molecular hydrogen under standard pressure (latm) and temperature (273K) is oxidised to solvated protons at the electrode.
Question 11.
Which metal is used to reduce $\mathrm{Cr}^{3+}$ ion? Why?
Answer:
A stable $\mathrm{Cr}^{3+}$ ion, strong reducing agent which has high negative value for reduction potential like metallic zinc $\left(\mathrm{E}^{\circ}=-0.76 \mathrm{~V}\right)$ is required. Metallic zinc is a powerful reducing agent due to its large negative values.
Question 12.
$\mathrm{Sc}^{3+}, \mathrm{Ti}^{4+}, \mathrm{V}^{5+}$ are diamagnetic. Give reason.
Answer:
1. $\mathrm{Sc}^{3+}, \mathrm{Ti}^{4+}, \mathrm{V}^{5+}$ have $\mathrm{d}^{\circ}$ electronic configuration, $\mathrm{n}=0$
2. $\mu=\sqrt{0(0+2)}=0 \mu_{\mathrm{B}}$ So they are diamagnetic.
Question 13.
Calculate the magnetic moment of $\mathrm{Ti}^{3+}$ and $\mathrm{V}^{4+}$.
Answer:
$
\begin{aligned}
& \mathrm{Ti}(\mathrm{Z}=22) \mathrm{Ti}^{3+} 3 \mathrm{~d}^1 \\
& \mathrm{~V}(\mathrm{Z}=23) \mathrm{V}^{4+} 3 \mathrm{~d}^1 \\
& \mu=\sqrt{1(1+2)}=\sqrt{35}=1.73 \mu_{\mathrm{B}} \text {. So they are paramagnetic. }
\end{aligned}
$
Question 14.
$\mathrm{Cr}^{3+}, \mathrm{Mn}^{4+}, \mathrm{V}^{2+}$ are paramagnetic. Calculate their magnetic moment values.
Answer:
$\mathrm{Cr}^{3+}, \mathrm{Mn}^{4+}, \mathrm{V}^{2+}$ Configuration is $\mathrm{d}^3$. Due to 3 unpaired electrons, they are paramagnetic. $\mu=\sqrt{3(3+2)}$ $=\sqrt{35}=3.87 \mu_{\mathrm{B}}$
Question 15.
$\mathrm{Mn}^{2+}, \mathrm{Fe}^{3+}$ have high magnetic moment. Prove it.
Answer:
1. $\mathrm{Mn}^{2+}, \mathrm{Fe}^{3+}$ configuration is $\mathrm{d}^5$.
2. $\mu=\sqrt{5(5+2)}=\sqrt{35}=5.916 \mu_{\mathrm{B}}$
Among $3 \mathrm{~d}$ series, $\mathrm{Mn}^{2+}, \mathrm{Fe}^{3+}$ have high magnetic moment as $5.916 \mu_{\mathrm{B}}$.
Question 16.
How many unpaired electrons are present in $\mathrm{CO}^{3+}, \mathrm{Fe}^{2+}$ ? Calculate their magnetic moment.
Answer:
$
\begin{aligned}
& \mathrm{CO}(\mathrm{Z}=27) \mathrm{CO}^{3+}[\mathrm{Ar}] 3 \mathrm{~d}^6 \\
& \mathrm{Fe}(\mathrm{Z}=26) \mathrm{Fe}^{2+}[\mathrm{Ar}] 3 \mathrm{~d}^6
\end{aligned}
$
The number of unpaired electrons are 4 as follows:
.png)
Their magnetic moment is $\mu=\sqrt{4(4+2)}=\sqrt{24}=4.89 \mu_{\mathrm{B}}$
Question 17.
Calculate the magnetic moment and the number of unpaired electrons in $\mathrm{Cu}^{2+}$.
Answer:
$\mathrm{Cu}(\mathrm{Z}=29)$ Electronic configuration $[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^1$
$\mathrm{Cu}^{2+}$ Electronic configuration [Ar] $3 \mathrm{~d}^9$
The number of unpaired electrons
.png)
Magnetic moment $\mu=\sqrt{1(1+2)}=\sqrt{3}=1.732 \mu_{\mathrm{B}}$
Question 18.
$\mathrm{Cu}^{+}, \mathrm{Zn}^{2+}$ are diamagnetic. Prove it.
Answer:
$\mathrm{Cu}^{+}, \mathrm{Zn}^{2+}$ electronic configuration [Ar] $3 \mathrm{~d}^{10}$
The number of unpaired electron is 0 .
$\mu=\sqrt{0(0+2)}=0 \mu_{\mathrm{B}} \cdot \mathrm{Cu}^{+}, \mathrm{Zn}^{2+}$ are diamagnetic.
Question 19.
Most of the transition metals act as catalyst. Justify this statement.
Answer:
1. Many industrial processes use transition metals or their compounds as catalysts. Transition metal has energetically available $d$ orbitals that can accept electrons from reactant molecule or metal can form bond with reactant molecule using its ' $d$ ' electrons.
2. For example, in the catalytic hydrogenation of an alkene, the alkene bonds to an active site by using its $n$ electrons with an empty d orbital of the catalyst.
Question 20.
Explain the catalytic hydrogenation of alkene to alkane with equation.
Answer:
The $\sigma$ bond in the hydrogen molecule breaks, and each hydrogen atom forms a bond with a d electron on an atom in the catalyst Nickel. The two hydrogen atoms then bond with the partially broken $\pi$-bond in the alkene to form an alkane.
.png)
Question 21.
Which catalyst is used in the hydroformylation of olefins? Give equation
Answer:
.png)
Question 22.
Which catalyst is used in the conversion of acetaldehyde to acetic acid? Give equation
Answer:
.png)
Question 23.
What is Zeigler -Natta catalyst? In which reaction it is used? Give equation.
Answer:
A mixture of $\mathrm{TiCl}_4$ and trialkyl aluminium is Zeigler-Natta catalyst. It is used in the polymerization
.png)
Question 24.
d-block elements readily form complexes. Give reason.
Answer:
1. Transition elements (d-block elements) have a tendency to form coordination compounds (complexes) with a species that has an ability to donate an electron pair to form a coordinate
2. Transition metal ions are small and highly charged and they have vacant low energy orbitals to accept an electron pair donated by other groups. Due to these properties, transition metals form large number of complexes.
3. Examples $-\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{4-},\left[\mathrm{CO}\left(\mathrm{NH}_3\right)_6\right]^{3+}$
Question 25.
Prove that acidified potassium dichromate is a powerful oxidising agent.
Answer:
$\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ act as power oxidising agent in acidic medium. In the presence of $\mathrm{H}^{+}$ions, the oxidation state of $\mathrm{Cr}$ froms $\mathrm{Cr}^{6+}$ is changed to $\mathrm{Cr}^{3+}$
$
\mathrm{Cr}_2 \mathrm{O}_7^{2-}+14 \mathrm{H}^{+}+6^{-} \rightarrow 2 \mathrm{Cr}^{3+}+6 \mathrm{Fe}^{3+}+7 \mathrm{H}_2 \mathrm{O}
$
Example:
Acidified $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ oxidises Ferrous salts to Ferric salts.
$
\mathrm{Cr}_2 \mathrm{O}_7^{2-}+6 \mathrm{Fe}^{2+}+14 \mathrm{H}^{+} \rightarrow 2 \mathrm{Cr}^{3+}+6 \mathrm{Fe}^{3+}+7 \mathrm{H}_2 \mathrm{O}
$
Question 26.
What are the uses of potassium dichromate?
Answer:
$\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ is used
1. as a strong oxidising agent
2. in dyeing and printing
3. in leather tanneries for chrome plating
4. in quantitative analysis for the estimation of iron compounds and iodides
Question 27.
Draw and explain about the structure of permanganate ion.
Answer:
.png)
Permanganate ion has tetrahedral geometry in which the central $\mathrm{Mn}^{7+}$ is $\mathrm{sp}^3$ hybridised.
Question 28 .
Explain the action of heat on potassium permanganate.
Answer:
.png)
Question 30.
What happens when thiosuiphate ion is treated with permanganate ion?
Answer:
Permanganate ion oxidises thiosulphate into sulphate.
$
8 \mathrm{MnO}_4^{-}+3 \mathrm{~S}_2 \mathrm{O}_3^{2-} \rightarrow 6 \mathrm{SO}_4^{2-}+8 \mathrm{MnO}_2+2 \mathrm{OH}^{-}
$
Question 31.
What is Baeyer's reagent? Where it is used?
Answer:
1. Cold dilute alkaline $\mathrm{KMnO}_4$ is known as Baeyer's reagent. It is used to oxidise alkene into diols.
2. For example, ethylene can be converted into ethylene glycol and this reaction is used as a test for unsaturation.
Question 32.
Acidified $\mathrm{KMnO}_4$ is a very strong oxidising agent. Prove it.
Answer:
1. In the presence of dilute sulphuric acid, potassium permanganate acts as a very strong oxidising agent. Permanganate ion is converted into $\mathrm{Mn}^{2+}$ ion.
$
\mathrm{MnO}_4^{-}+8 \mathrm{H}^{+}+5 \mathrm{e}^{-} \rightarrow \mathrm{Mn}^{2+}+4 \mathrm{H}_2 \mathrm{O}
$
2. Permanganate oxidises ferrous salt to ferric salt.
$
2 \mathrm{MnO}_4^{-}+10 \mathrm{Fe}^{2+}+16 \mathrm{H}^{+} \rightarrow 2 \mathrm{Mn}^{2+}+10 \mathrm{Fe}^{3+}+8 \mathrm{H}^2 \mathrm{O}
$
Question 33.
$\mathrm{KMnO}_4$ does not act as oxidising agent in the presence of $\mathrm{HCl}$. Why?
Answer:
$\mathrm{HCl}$ cannot be used for making acidified $\mathrm{KMnO}_4$ as oxidising agent, since it reacts with $\mathrm{KMnO}_4$ as follows.
$
2 \mathrm{MnO}_4^{-}+10 \mathrm{Cl}^{-}+16 \mathrm{H}^{+} \rightarrow 2 \mathrm{Mn}^{2+}+5 \mathrm{Cl}_2+8 \mathrm{H}_2 \mathrm{O}
$
Question 34 .
$\mathrm{HNO}_3$ cannot be used as an acid medium along with $\mathrm{KMnO}_4$. Why?
Answer:
$\mathrm{HNO}_3$ cannot be used since it is a good oxidising agent and it reacts with reducing agents in the reaction.
Question 35 .
Among $\mathrm{HCl}, \mathrm{HNO}_3$ and $\mathrm{H}_2 \mathrm{SO}_4$, which is the suitable medium for $\mathrm{KMnO}_4$ in oxidising reaction?
$\mathrm{HCl}$ and $\mathrm{HNO}_3$ cannot be used. $\mathrm{HCl}$ react with $\mathrm{KMnO}_4 . \mathrm{HNO}_3$ is itself a good oxidising agent. However, $\mathrm{H}_2 \mathrm{SO}_4$ is found to be most suitable since it does not react with potassium permanganate.
Question 36.
Explain about the causes of lanthanide contraction.
Answer:
1. As we move from one element to another in $4 \mathrm{f}$ series ( $\mathrm{Ce}$ to $\mathrm{Lu}$ ) the nuclear charge increases by one unit and an additional electron is added into the same inner $4 \mathrm{f}$ sub-shell.
2. $4 \mathrm{f}$ sub-shell have a diffused shapes and therefore the shielding effect of $4 \mathrm{f}$ electrons are relatively poor. Hence, with increase of nuclear charge, the valence shell is pulled slightly towards nucleus.
3. As a result, the effective nuclear charge experienced by the 4 elelctoms increases and the size of $\operatorname{Ln}^{3+}$ ions decreases.
3 Mark Questions andAnswers
Question 1.
$\mathrm{Cr}$ and $\mathrm{Cu}$ are more stable. Give reason.
Answwer:
1. The electronic configuration of $\mathrm{Cr}$ and $\mathrm{Cu}$ are [ $\mathrm{Ar}] 3 \mathrm{~d}^3 4 \mathrm{~s}^1$ and $[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^1$ respectively. The extra stability of half filled and fully filled d orbitals, as already explained in XI STD, is due to symmetrical distribution of electrons and exchange energy.
2. The extra stability of half filled and fully filled d orbitals is due to symmetrical distribution of electrons and exchange energy.
3. When the $d$ orbitals are considered together, they will constitute a sphere. So the half filled and fully filled configuration leads to complete symmetrical distribution of electron density.
4. On the other hand, an unsymmetrical distribution of electron density will result in building up of a potential difference. To decrease this and to achieve a tension free state with lower energy, a symmetrical distribution is preferred.
Question 2.
Explain about the metallic behaviour of d-block elements.
Answer:
1. All the transition elements are metals. They are good conductors of heat and electricity. Of all the known elements, silver has the highest electrical conductivity at room temperature.
2. Most of the transition elements are hexagonal close packed, cubic close packed or body centered cubic which are the characteristics of true metals.
Question 3.
Explain about the variation of melting point among the transition metal series.
Answer:
1. As we move from left to right along the transition metal series, melting point first increases as the number of unpaired d electrons available for metallic bonding increases, reach a maximum value and then decreases, as the delectron pairs up and become less available for bonding.
2. For example, in the first series the melting point increases from Scandium to a maximum of $2183 \mathrm{~K}$ for Vanadium, which is close to $2180 \mathrm{~K}$ for chromium.
3. Manganese in $3 \mathrm{~d}$ series and has low melting point. The maximum melting point at about the middle of transition metal series indicates that $\mathrm{d}^5$ configuration is favorable for strong interatomic attraction.
Question 4.
Explain about the variation of atomic radius along a period of $3 \mathrm{~d}$ series.
Answer:
1. In general, atomic radius decreases along a period. But for the $3 \mathrm{~d}$ transition elements, the expected decrease in atomic radius is observed from $\mathrm{Sc}$ to $\mathrm{V}$, thereafter upto $\mathrm{Cu}$ the atomic radius nearly remains the same.
2. As we move from $\mathrm{Sc}$ to $\mathrm{Zn}$ in $3 \mathrm{~d}$ series, the extra electrons are added to the $3 \mathrm{~d}$ orbitals, the added $3 \mathrm{~d}$ electrons only partially shield the increased nuclear charge and hence the effective nuclear charge increases slightly.
3. However, the extra electrons added to the $3 \mathrm{~d}$ sub shell strongly repel the 4 s electrons and these two forces are operated in opposite direction and as they tend to balance each other, it leads to constancy in atomic radii.
Question 5.
Ni (II) compounds are more stable than Pt (II) compounds. Give reason.
1. The ionisation enthalpy values can be used to predict the thermodynamic stability of their compounds. .
2. For Nickel I.E $\mathrm{I}_1+\mathrm{I} . \mathrm{E}_2=737+1753$
$=2490 \mathrm{~kJ} \mathrm{~mol}^{-1}$
For platinum, I.E $\mathrm{I}_1+\mathrm{I} \cdot \mathrm{E}_2=864+1791$
$=2655 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Since, the energy required to form $\mathrm{Ni}^{2+}$ is less than that of $\mathrm{Pt}^{2+}, \mathrm{Ni}$ (II) compounds are thermodynamically more stable than Pt(II) compounds.
Question 6.
Compare the reduction potentials of $\mathrm{Mn}^{3+} / \mathrm{Mn}^{2+}$ and $\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}$.
Answer:
$
\begin{aligned}
& 1 . \mathrm{Mn}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Mn}^{2+} \\
& \mathrm{E}^{\circ}=+1.51 \mathrm{~V} \\
& \mathrm{Fe}^{3+}+\mathrm{e}^{-} \rightarrow \mathrm{Fe}^{2+} \\
& \mathrm{E}^{\circ}=+0.77 \mathrm{~V}
\end{aligned}
$
2. The high reduction potential of $\mathrm{Mn}^{3+} / \mathrm{Mn}^{2+}$ indicates $\mathrm{Mn}^{2+}$ is more stable than $\mathrm{Mn}^{3+}$. For $\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}$ the reduction potential is $0.77 \mathrm{~V}$, this low value indicates that both $\mathrm{Fe}^{3+}$ and $\mathrm{Fe}^{2+}$ can exist under normal conditions.
3. The drop from $\mathrm{Mn}$ to $\mathrm{Fe}$ is due to the electronic structure of the ions concerned. $\mathrm{Mn}^{3+}$ has $3 \mathrm{~d}^4$ configuration while that of $\mathrm{Mn}^{2+}$ is $3 \mathrm{~d}^5$. The extra stability associated with a half filled d sub-shell makes the reduction of $\mathrm{Mn}^{3+}$ very feasible.
Question 7.
How alloys are formed in d-biock elements?
Answer:
1. An alloy is formed by blending a metal with one or more other elements. The elements may be metals or non-metals or both.
2. The bulk metal is named as solvent, and the other elements in smaller portion is called solute.
3. According to Hume - Rothery rule to form an alloy, the difference between the atomic radii of the solvent and solute is less than $15 \%$. Both the solvent and solute must have the same crystal structure and valence and their electro negativity difference must be close to zero.
4. Since their atomic sizes are similar and one metal atom can be easily replaced by another metal atom from its crystal lattice to form an alloy. The alloys are hard and have high melting points. Examples - Gold - copper alloy.
Question 8.
What are interstitial compounds? Give their properties.
Answer:
An interstitial compound or alloy is a compound that is formed when small atoms like hydrogen, boron, carbon or nitrogen are trapped in the interstitial holes in a metal lattice. They are usually nonstoichiometric compounds, e.g., $\mathrm{TiC}, \mathrm{ZrH}_{1.92}, \mathrm{Mn}_4 \mathrm{~N}$.
1. They are hard and show electrical and thermal conductivity.
2. They have high melting points.
3. Transition metal hydrides are used as powerful reducing agents.
4. Metallic carbides are chemically inert.
Question 9.
Explain the action of heat on potassium dichromate.
Answer:
$
4 \mathrm{~K}_2 \mathrm{Cr}_2 \mathrm{O}_7 \stackrel{\Delta}{\longrightarrow} 4 \mathrm{~K}_2 \mathrm{CrO}_4+2 \mathrm{Cr}_2 \mathrm{O}_3+3 \mathrm{O}_2 \uparrow
$
Potassium dichromate Potassium chromate Chromic oxide
Question10.
Draw and explain about the structure of chromate and dichromate ion.
Answer:
.png)
1. Both chromate and dichromate ions are oxo anions of chromium and they are moderately strong oxidising agents.
2. In both structures, chromium is in +6 oxidation state.
3. In an aqueous solution, chromate and dichromate ions can be inter convertible, and in an alkaline solution, chromate ion is predominant, whereas dichromate ion becomes predominant in acidic solutions. .
Question 11.
Explain the action of acidified $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7-$ with
1. Iodide
2. Sulphide
Answer:
1. Acidified $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ oxidises iodide ions to iodine.
$
\mathrm{Cr}_2 \mathrm{O}_7^{2-}+6 \mathrm{I}^{-}+14 \mathrm{H}^{+} \rightarrow 2 \mathrm{Cr}^{3+}+3 \mathrm{I}_2+7 \mathrm{H}_2 \mathrm{O}
$
2. Acidified $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ oxidises Sulphide ions to Sulphur.
$
\mathrm{Cr}_2 \mathrm{O}_7^{2-}+3 \mathrm{~S}^{2-}+14 \mathrm{H}^{+} \rightarrow 2 \mathrm{Cr}^{3+}+3 \mathrm{~S}+7 \mathrm{H}^2 \mathrm{O}
$
Question 12.
Explain the action of acidified $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ with
1. Sulphur dioxide
2. Alcohols.
Answer:
1. Acidified $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ oxidises $\mathrm{SO}_2$ to sulphate ion.
$
\mathrm{Cr}_2 \mathrm{O}_7^{2-}+3 \mathrm{SO}^2+2 \mathrm{H}^{+}->2 \mathrm{Cr}^{3+}+3 \mathrm{SO}_4^{2-}+\mathrm{H}_2 \mathrm{O}
$
2. Acidified $\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7$ oxidises alcohol to acid..
.png)
Question 13.
Explain about chromyl chloride test.
Answer:
1. When potassium dichromate is heated with any chloride salt in the presence of $\mathrm{Conc}_2 \mathrm{H}_2 \mathrm{SO}_4$, orange red vapours of chromyl chloride $\left(\mathrm{CrO}_2 \mathrm{Cl}_2\right)$ is evolved. This reaction is used to confirm the presence of chloride ion in inorganic qualitative analysis.
.png)
2. The chromyl chloride vapours are dissolved in sodium hydroxide solution and then acidified with acetic acid and treated with lead acetate. A yellow precipitate of lead chromate is obtained.
.png)
Question 14.
Explain the action of Conc. $\mathrm{H}_2 \mathrm{SO}_4$ on potassium permanganate.
Answer:
1. On treating with cold conc. $\mathrm{H}_2 \mathrm{SO}_4$, it decomposes to form manganese heptoxide, which subsequently
decomposes explosively.
.png)
2. With hot Conc. $\mathrm{H}_2 \mathrm{SO}_4$, potassium permanganate give $\mathrm{MnSO}_4$ [Manganese(II) sulphate] $
.png)
Question 15 .
What are the uses of Potassium permanganate?
Answer:
Potassium permanganate is used,
1. as a strong oxidising agent.
2. for the treatment of various skin infections and fungal infections of foot.
3. used in water treatment industries to remove iron and hydrogen sulphide from well water.
4. as a Baeyer's reagent for detecting unsaturation in an organic compound.
5. in quantitative analysis for the estimation of ferrous salts, oxalates, hydrogen peroxide $\left(\mathrm{H}_2 \mathrm{O}_2\right)$ and iodides.
Question 16.
Calculate the equivalent weight of $\mathrm{KMnO}_4$ in
1. Acidic medium
2. Basic medium
3. Neutral medium
Answer:
1. Equivalent weight of $\mathrm{KMnO}_4$ in acidic medium
$=\frac{\text { Molecular weight of } \mathrm{KMnO}_4}{\text { No. of moles of electrons transferred }}$
2. Equivalent weight of $\mathrm{KMnO}_4$ in basic medium
$=\frac{\text { Molecular weight of } \mathrm{KMnO}_4}{\text { No. of moles of electrons transferred }}$
3. Equivalent weight of $\mathrm{KMnO}_4$ in neutral medium
$=\frac{\text { Molecular weight of } \mathrm{KMnO}_4}{\text { No. of moles of electrons transferred }}$
Question 17.
Explain about the oxidation state of actinoids.
Answer:
1. The most common oxidation state of actinoids is +3 .
2. In addition to that actinoids show variable oxidation states such as $+2,+3,+4,+5,+6$ and +7 .
3. The elements Americium (Am) and Thorium (Th) show +2 oxidation state in some compounds.
4. $\mathrm{Th}, \mathrm{Pa}, \mathrm{U}, \mathrm{Np}, \mathrm{Pu}$ and $\mathrm{Am}$ show +5 oxidation states.
5. $\mathrm{Np}$ and $\mathrm{Pu}$ exhibit +7 oxidation state.
Question 18 .
Write the electronic configuration of
1. Ac $(\mathrm{Z}=89)$
2. $\operatorname{Am}(Z=95)$
3. $\operatorname{Lr}(\mathrm{Z}=103)$
Answer:
1. $\operatorname{Ac}(Z=89):[\mathrm{Rn}] 5 f^0 6 d^1 7 s^2$
2. $\operatorname{Am}(\mathrm{Z}=95):[\mathrm{Rn}] 5 \mathrm{f}^7 6 \mathrm{~d}^0 7 \mathrm{~s}^2$
3. $\operatorname{Lr}(Z=103):[R n] 5 f^{14} 6 d^1 7 s^2$
5 Mark Questions and Answers
Question 1.
Explain about the magnetic properties of transition elements.
Answer:
1. Most of the compounds of transition elements are paramagnetic.
2. Materials with no elementary magnetic dipoles are diamagnetic. In other words a species with all paired electrons exhibits diamagnetism.
3. Paramagnetic solids having unpaired electrons possess magnetic dipoles which are isolated from one another.
4. Ferromagnetic materials have domain structure and in each domain the magnetic dipoles are arranged. But the spin dipoles of the adjacent domains are randomly oriented. Some transition elements or ions with unpaired d electrons show ferromagnetism.
5. $3 \mathrm{~d}$ transition metal ions in paramagnetic solids often have a magnetic dipole moments corresponding to the electron spin contribution only. So the magnetic moment of the ion is given by $\mu=g \sqrt{S(S+1)} \mu_{\mathrm{B}}$
Where $g=2, S$ is the total spin quantum number of the electrons.
$\mu_{\mathrm{B}}=$ Bohr Magneton.
For an ion with ' $n$ ' unpaired electrons $S=\frac{n}{2}$
Therefore the spin only magnetic moment is $\mu=2 \sqrt{\left(\frac{n}{2}\right)\left(\frac{n}{2}+1\right)} \mu_{\mathrm{B}}$
$
\begin{aligned}
& \mu=2 \sqrt{\left(\frac{n(n+2)}{4}\right)} \mu_{\mathrm{B}} \\
& \mu=2 \sqrt{n(n+2)} \mu_{\mathrm{B}}
\end{aligned}
$
Question 2.
How will you prepare potassium permanganate from pyrolusite ore?
Answer:
Potassium permanganate is prepared from pyrolusite $\left(\mathrm{MnO}_2\right)$ ore. The preparation involves the following steps.
1. Conversion of $\mathrm{MnO}_2$ to potassium manganate:
Powdered ore is fused with $\mathrm{KOH}$ in the presence of air or oxidising agents like $\mathrm{KNO}_3$. A green coloured potassium manganate is formed.
.png)
2. Oxidation of potassium manganate to potassium permanganate:
Potassium manganate can be oxidised in two ways, either by chemical oxidation or electrolytic oxidation.
3. Chemical oxidation - In this method potassium manganate is treated with ozone $\left(\mathrm{O}_3\right)$ or chlorine to get potassium permanganate.
$
\begin{aligned}
& 2 \mathrm{MnO}_4^{2-}+\mathrm{O}_3+\mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{MnO}_4^{2-}+2 \mathrm{OH}^{-}+\mathrm{O}_2 \\
& 2 \mathrm{MnO}_4^{2-}+\mathrm{Cl}_2 \rightarrow 2 \mathrm{MnO} \mathrm{O}_4^{2-}+2 \mathrm{Cl}^{-}
\end{aligned}
$
4. Electrolytic oxidation: In this method aqueous solution of potassium manganate is electrolyzed in the presence of little alkali.
$
\begin{aligned}
& \mathrm{K}_2 \mathrm{MnO}_4 \equiv 2 \mathrm{~K}^{+}+2 \mathrm{MnO}_4^{2-} \\
& \mathrm{H}_2 \mathrm{O} \equiv \mathrm{H}^{+}+\mathrm{OH}^{-}
\end{aligned}
$
Manganate ions are converted into permanganate ions at anode.
$\mathrm{H}_2$ is liberated at the cathode.
$
2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \rightarrow \mathrm{H}_2 \uparrow
$
The purple coloured solution is concentrated by evaporation and forms crystals of potassium permanganate Question 3.
Explain acidified $\mathrm{KMnO}_4$ is a powerful oxidising agent with 5 examples.
Answer:
1. In the presence of dilute sulphuric acid, potassium permanganate acts as a very strong oxidising agent. Permanganate ions is converted into $\mathrm{Mn}^{2+}$ ion.
$
\mathrm{MnO}_4^{-}+8 \mathrm{H}^{+}+5 \mathrm{e}^{-} \rightarrow \mathrm{Mn}^{2+}+4 \mathrm{H}_2 \mathrm{O}
$
Example:
1. Potassium permanganate oxidises ferrous salts to ferric salts.
.png)
2. Potassium permanganate oxidises iodide ions to iodine.
$
2 \mathrm{MnO}_4^{-}+10 \mathrm{I}+16 \mathrm{H}^{+} \rightarrow 2 \mathrm{Mn}^{2+}+5 \mathrm{I}^2+8 \mathrm{H}^2 \mathrm{O}
$
3. Potassium permanganate oxidises sulphide ion to sulphur.
$
2 \mathrm{MnO}_4^{-}+5 \mathrm{~S}^{2-}+16 \mathrm{H}^{+} \rightarrow 2 \mathrm{Mn}^{2+}+5 \mathrm{~S}+8 \mathrm{H}^2 \mathrm{O}
$
4. Potassium permanganate oxidises oxalic acid to $\mathrm{CO}_2$.
$
2 \mathrm{MnO}_4^{-}+5(\mathrm{COO})^{2-}+16 \mathrm{H}^{+} \rightarrow 2 \mathrm{Mn}^{2+}+10 \mathrm{CO}_2+8 \mathrm{H}_2 \mathrm{O}
$
5. Potassium permanganate oxidises alcohols to aldehyde.
$
2 \mathrm{KMnO}_4+3 \mathrm{H}_2 \mathrm{SO}_4+5 \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OH} \rightarrow 2 \mathrm{~K}_2 \mathrm{SO}_4+2 \mathrm{MnSO}_4+5 \mathrm{CH}_3 \mathrm{CHO}+8 \mathrm{H}_2 \mathrm{O}
$
Question 4 .
Explain about the oxidation state of Lanthanoids.
Answer:
1. The common oxidation state of lanthanoids is +3 . In addition to that some of the lanthanoids also show either +2 or +4 oxidation states.
2. $\mathrm{Gd}^{3+}$ and $\mathrm{Lu}^{3+}$ ions have extra stability, it is due to half filled and completely filled f-orbitals.
3. Cerium and terbium attain $4 \mathrm{f}^7$ and $4 \mathrm{f}^{14}$ configurations respectively in the +4 oxidation states.
4. $\mathrm{Eu}^{2+}$ and $\mathrm{Yb}^{2+}$ ions have exactly half filled and completely filled $\mathrm{f}$ orbitals.
5. Lu shows only +3 oxidation state.
6. $\mathrm{Ce}, \mathrm{Pr}, \mathrm{Nd}, \mathrm{Tb}$ and Dy exhibit +3 and +4 oxidation states.
7. $\mathrm{Nd}, \mathrm{Sm}, \mathrm{Eu}, \mathrm{Tm}, \mathrm{Yb}$ exhibit +2 oxidation states also.
Common Errors:
Atomic number of d-block elements may get confused.
Rectifications:
Atomic number of d-block elements in group wise jumped as $18,18,18,32$.
e.g. Sc $(Z=21)$
$Y(Z=39)$
$\mathrm{La}(Z=57)$
$\operatorname{Ac}(Z=89)$
