Page No 56: - Chapter 4 - Structure Of Atom - Ncert Solutions class 9 - Science
Updated On 26-08-2025 By Lithanya
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Question 18:
Which one of the following is a correct electronic configuration of sodium?
(a) 2, 8
(b) 8, 2, 1
(c) 2, 1, 8
(d) 2, 8, 1
Answer:
(d) The correct electronic configuration of sodium is 2, 8, 1.
Question 19:
Complete the following table.
|
Atomic number |
Mass number |
Number of Neutrons |
Number of protons |
Number of electrons |
Name of the Atomic species |
|
9 |
− |
10 |
− |
− |
− |
|
16 |
32 |
− |
− |
− |
Sulphur |
|
− |
24 |
− |
12 |
− |
− |
|
− |
2 |
− |
1 |
− |
− |
|
− |
1 |
0 |
1 |
0 |
− |
Answer:
|
Atomic number |
Mass number |
Number of Neutrons |
Number of protons |
Number of electrons |
Name of the Atomic species |
|
9 |
19 |
10 |
9 |
9 |
Fluorine |
|
16 |
32 |
16 |
16 |
16 |
Sulphur |
|
12 |
24 |
12 |
12 |
12 |
Magnesium |
|
1 |
2 |
1 |
1 |
1 |
Deuterium |
|
1 |
1 |
0 |
1 |
0 |
Hydrogen ion |
