Question

Which of the following correctly represents the electronic distribution in the Mg atom?

• A. 3,8,1
• B. 2,8,2
• C. 1,8,3
• D. 8,2,2

Answer 1

The correct option is B

2,8,2

Electronic configuration:

1. The maximum number of electrons in orbit is calculated by $2{\mathrm{n}}^2$, where ‘n’ is the number of orbits.
2. K shell occupies a maximum of two electrons.
3. L shell occupies a maximum of eight electrons.
4. M shell occupies a maximum of eighteen electrons.
5. Electrons only occupy the next orbit only after filling the inner orbit completely.

Explanation:

The atomic number of magnesium is 12. The electronic configuration of magnesium is 2,8,2. So, option b) is the correct answer.

Option a) 3,8,1 is incorrect because the first shell can only have two electrons.

Option c) 1,8,3 is incorrect because the first shell is not completely filled. It must contain two electrons.

Option d) 8,2,2 is incorrect because the first shell has one orbital in which two electrons can be filled.

Hence, option b) is the correct answer.