Among the following groups, select the species which has the smallest

Dhanalakshmi · July 17, 2019, 9:47am

Among the following groups, select the species which has the smallest radius. Also, give appropriate reasons to support your answer.
i) O, O^-, O^2-
ii) K⁺, Sr²⁺, Ar
iii) Si, P, Cl

Dhanalakshmi · July 17, 2019, 9:48am

i) Among O, O^-, O^2- the species O has the smallest radii because the radius of the anion is always larger than the radius of the atom from which it is formed. O^- and O^2- are anions of oxygen.

ii) In K⁺ and Ar the outer most shell is third where as in Sr²⁺ it is fourth. Out of K⁺, Sr²⁺ and Ar, K⁺ has smaller size because it has greater nuclear charge.

iii) Among Si, P and Cl, Cl has the smallest radius. Si, P and Cl belong to the same period. In a period the atomic radius decreases with increase in atomic number due to increase in the effective nuclear charge.