Question

Arrange Ce³⁺, La³⁺, Pm³⁺ and Yb³⁺ in increasing order of their ionic radii.
(a) Yb³⁺ < Pm³⁺ < Ce³⁺ < La³⁺
(b) Ce³⁺ < Yb³⁺ < Pm³⁺ < La³⁺
(c) Yb³⁺ < Pm³⁺ < La³⁺ < Ce³⁺
(d) Pm³⁺ < La³⁺ < Ce³⁺ < Yb^{3+ .}

Answer 1

(a) : According to their positions in the periods, these values are in the order: