Question

Choose the correct option for the electronic configuration of magnesium:

• A. $\left[\mathrm{Ne}\right]3{\mathrm{s}}^2$,
• B. $4{\mathrm{f}}^{14}5{\mathrm{d}}^{10}6{\mathrm{s}}^1$,
• C. $4{\mathrm{d}}^{10}5{\mathrm{s}}^1$,
• D. $\left[\mathrm{He}\right]2{\mathrm{s}}^{2}2{\mathrm{p}}^2$,

Answer 1

The correct option is A

$\left[\mathrm{Ne}\right]3{\mathrm{s}}^2$,

Explanation for correct option

(a) $\left[\mathrm{Ne}\right]3{\mathrm{s}}^2$

• The atomic number of magnesium is $12$.
• According to Aufbau Principle, the electronic configuration of magnesium will be written as $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2$.
• Electronic configuration of previous noble gas $\left(\mathrm{Ne}\right)$ of magnesium is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^6$.
• Hence the electronic configuration of magnesium can be written as $\left[\mathrm{Ne}\right]3{\mathrm{s}}^2$.
• Hence the correct option is (a) $\left[\mathrm{Ne}\right]3{\mathrm{s}}^2$.

Explanation for incorrect options

Since, the correct electronic configuration is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^6$ or $\left[\mathrm{Ne}\right]3{\mathrm{s}}^2$. Therefore, options (b), (c) and (d) are incorrect.

Hence, the correct option is (a) $\left[\mathrm{Ne}\right]3{\mathrm{s}}^2$