Ncert Exercises & Solutions

3.24 Describe the theory associated with the radius of an atom as it

(a) gains an electron

(b) loses an electron

(a)When an atom gains an electron, its size increases. When an electron is added, the

number of electrons goes up by one. This results in an increase in repulsion among the

electrons. However, the number of protons remains the same. As a result, the effective

nuclear charge of the atom decreases and the radius of the atom increases.

(b)When an atom loses an electron, the number of electrons decreases by one while the

nuclear charge remains the same. Therefore, the interelectronic repulsions in the atom

decrease. As a result, the effective nuclear charge increases. Hence, the radius of the atom

decreases.