Question

Variation of atomic radius.

Answer 1

Along a period – size decreases from left to right due to increase in effective nuclear charge.

Size of inert gases are larger than halogens. In inert gases all orbitals are completely filled, inter electronic repulsions are maximum. Measured in terms of Vanderwaals radius

Down the group – size increases due to addition of a new energy shell at each succeeding element.

Ionic radius – effective distance from the centre of the nucleus of the ion upto which it exerts its influence on its electronic cloud.

Radius of cation is always smaller than parent atom – size of Mg²⁺ is smaller than Mg due to increase in effective nuclear charge.

Radius of anion is always larger than parent atom – size of Cl is larger than Cl due to decrease in effective nuclear charge.

Variation of ionic radius among isoelectronic species

Al³⁺ < Mg²⁺ < Na⁺ < F < O^2- < N^3-

As the effective nuclear charge increases, size decreases