Home Chemistry Structure of Atom Quantum Number, Electronic Configuration and Shape of Orbitals Three elements ‘X’, ‘Y’ and ‘Z’ have atomic …
Chemistry Structure of Atom Quantum Number, Electronic Configuration and Shape of Orbitals Single Correct MCQ
Published on: August 13, 2026

Three elements ‘X’, ‘Y’ and ‘Z’ have atomic numbers 18, 19 and 20 respectively. how many electrons are present in the M shells of these elements?

A
8, 9, 10
B
8, 10, 13
C
8, 8, 8
D
8, 9, 12

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Text Solution

Verified by Experts
The correct answer is:
C

M shell means it is third shell
For element X : atomic number
thus its electronic configuration:
Electrons in M shell=2+6=8
For element Y : atomic number
thus its electronic configuration:
Electrons in M shell=2+6=8
For element : atomic number
thus its electronic configuration:
Electrons in M shell=2+6=8
thus in element the number of electrons in shell is respectively.

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