Question

Why is the positive ion always smaller than the corresponding neutral atom?

Answer 1

• In a neutral atom, the number of protons is equal to the number of electrons.
• When a neutral atom loses its electrons, becomes a positively charged ion i.e., cation.
• While in a cation, the number of protons is greater than the number of electrons.
• The effective nuclear charge acting on the electrons of a cation is greater than that acting on a neutral atom.
• Hence, the positive ion is always smaller than the corresponding neutral atom.
• For example - Sodium ion $\left({\mathrm{Na}}^{+}\right)$ is smaller in size compared to a Sodium atom.