Question

If Aufbau rule is violated, then $C{a}^{20}$ will be in:

• A. p-block
• B. s-block
• C. d-block
• D. f-block

Answer 1

Answer: (C)

According to the Aufbau principle, electron enters into the lowest energy level (orbital), before entering into a higher energy level. Hence, according to this principle, the electronic configuration of $C{a}^{20}$ is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^2$, as differentiating electron enters into the s-orbital, $Ca$ belongs to s-block.

If we don't follow the Aufbau rule, the electronic configuration of $C{a}^{20}$ would be $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^2$.

Here, the differentiating electron is entering in the d orbital, so it would belong to the d-block element.