NCERT Solutions for Class 9 Science Chapter 4
Structure of the Atom
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Intext Questions
Page No-53
Questions No-2
Write the electronic configuration of any one pair of isotopes and isobars.
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Isotopes:
Isotopes are atoms of the same element that have the same number of protons (hence the same atomic number) but differ in the number of neutrons. The electronic configuration of isotopes remains the same since they share the same number of protons and electrons.
For instance, considering hydrogen isotopes:
– Hydrogen-1 (^1H): Electronic configuration – 1s¹
– Deuterium (^2H): Electronic configuration – 1s¹
**Isobars:**
Isobars are atoms of different elements that have the same mass number (total number of protons and neutrons) but different atomic numbers. As a result, they have different electronic configurations.
For example, comparing carbon-14 (^14C) and nitrogen-14 (^14N):
– Carbon-14 (^14C): Electronic configuration – 1s² 2s² 2p²
– Nitrogen-14 (^14N): Electronic configuration – 1s² 2s² 2p³
Two isotopes of carbon are ¹²₆𝐶 and ¹⁴₆𝐶
The electronic configuration of ¹²₆𝐶 is 2, 4.
The electronic configuration of ¹⁴₆𝐶 is 2, 4.
[Isotopes have same electronic configuration]
⁴⁰₂₉𝐶𝑎 and ⁴⁰₁₈𝐴𝑟 are a pair of isobars
The electronic configuration of ⁴⁰₂₉𝐶𝑎 is 2, 8, 8, 2
The electronic configuration of ⁴⁰₁₈𝐴𝑟 is 2, 8, 8.
[Isobars have different electronic configuration]
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