Question

Which of the following arrangements does not represent the correct order of the property stated against it?

Options

• V²⁺ < Cr²⁺ < Mn²⁺ < Fe²⁺: paramagnetic behaviour

• Ni²⁺ < Co²⁺ < Fe²⁺ < Mn²⁺: ionic size

• Co³⁺ < Fe³⁺ < Cr³⁺ < Sc³⁺: stability in aqueous solution

• Sc < Ti < Cr < Mn: number of oxidation states

Answer 1

V²⁺ < Cr²⁺ < Mn²⁺ < Fe²⁺: paramagnetic behaviour

Explanation:

V = 3d³ 4s²; V²⁺ = 3d³ = 3 unpaired electrons

Cr = 3d⁵ 4s¹; Cr²⁺ = 3d⁴ = 4 unpaired electrons

Mn = 3d⁵ 4s²; Mn²⁺ = 3d⁵ = 5 unpaired electrons

Fe = 3d⁶ 4s²; Fe²⁺ = 3d⁶ = 4 unpaired electrons

Hence the correct order of paramagnetic behaviour:

V²⁺ < Cr²⁺ = Fe²⁺ < Mn²⁺