Structure of Atom — Chemistry STD 11 Science — Question

3. D-block

Explanation:

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 Ca²⁰ is 1s²2s²2p⁶3s²3p⁶4s², 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 Ca²⁰ would be 1s²2s²2p⁶3s²3p⁶3d².