Question

Ce³⁺, La³⁺, Pm³⁺ and Yb³⁺ have ionic radii in the increasing order as ______.

Options

• La³⁺ < Ce³⁺ < Pm³⁺ < Yb³⁺

• Yb³⁺ < Pm³⁺ < Ce³⁺ < La³⁺

• La³⁺ = Ce³⁺ < Pm³⁺ < Yb³⁺

• Yb³⁺ < Pm³⁺ < La³⁺ < Ce³⁺

Answer 1

Ce³⁺, La³⁺, Pm³⁺ and Yb³⁺ have ionic radii in the increasing order as Yb³⁺ < Pm³⁺ < Ce³⁺ < La³⁺.

Explanation:

All the given ions are lanthanoid ions in the +3 oxidation state. In the lanthanoid series, ionic size decreases from left to right due to lanthanoid contraction. This happens because 4f-electrons have a poor shielding effect, so the nuclear charge increases and pulls electrons closer. Order of the elements in the series is Lu(57), Ce(58), Pm(61), and Yb(71).