Question

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

• A. (a) 3, 8, 1
• B. (b) 2, 8, 2
• C. (d) 8, 2, 2
• D. (c) 1, 8, 3

Answer 1

The correct option is B

(b) 2, 8, 2

The explanation for the correct option

(b) 2, 8, 2

• The magnesium atom has a total of $12$ electrons.
• Magnesium's electron arrangement is, Mg ($1{\mathrm{s}}^2,2{\mathrm{s}}^2,2{\mathrm{p}}^6,3{\mathrm{s}}^2$) with Z=$12$
• The 1s orbital occupies the first two electrons as the $\mathrm{s}$ orbital occupies not more than $2$ electrons.
• The following two electrons are located in the $2\mathrm{s}$ orbital. As the p orbital can have a maximum of 6 electrons, so the next $6$ electrons are located in the $\mathrm{p}$ orbital.
• The final two electrons are located in the $3\mathrm{s}$ orbital.
• Hence, option (b) is correct.

The explanation for incorrect options

(a) 3, 8, 1

• The s orbital always comprises of $2$ electrons and here the s orbital is having $3$ electrons, which is not possible.
• Hence, option (a) is incorrect.

(c ) 1, 8, 3

• The s orbital is comprised of $3$ orbital which is not possible.
• Hence, option (c ) is incorrect.

(d) 8, 2 , 2

• The s orbital cannot have more than $2$ electrons; here there are $8$ electrons.
• Therefore, option (d) is incorrect

Hence, option (b) is the correct option.