Consider the following complex ions, P, Q and R: P = [FeF₆]³⁻, Q = [V(H₂O)₆]²⁺ and R = [Fe(H₂O)₆]²⁺. The correct order of the complex ions, according to their spin-only magnetic moment values (in B.M.) is ___________.

P = Fe³⁺ (no. unpaired e⁻ = 5)
Q = V²⁺ (no. of unpaired e⁻ = 3)
R = Fe²⁺ (no. unpaired e⁻ = 4)
As all ligands are weak field, hence the no. of unpaired electrons remains the same in the complex ion.
μ = √n(n+2) B.M. where n is the number of unpaired electrons.
Hence (B) is correct.