Question

The correct order of size of the three species $Ca,$ $C{a}^{+}$ and $C{a}^{2+}$ is :

• A. $Ca>C{a}^{+}>C{a}^{2+}$
• B. $C{a}^{2+}>C{a}^{+}>Ca$
• C. $C{a}^{+}>Ca>C{a}^{2+}$
• D. $C{a}^{+}>C{a}^{2+}>Ca$

Answer 1

The correct option is A $Ca>C{a}^{+}>C{a}^{2+}$

Cations are smaller than the respective atoms because when an electron is lost, electron-electron repulsion decreases and thus shielding increases. Therefore, the nuclear pull towards the valence electron increases. In $C{a}^{2+}$, two electrons are lost and thus the shielding further decreases and nuclear attraction for valence electrons is even more.

Thus, the order of size can be written as; $Ca>C{a}^{+}>C{a}^{2+}$.