Number of complexes from the following with even number of unpaired " ( d ) " electrons is ( ) ( [ V ( H ₂ O )₆ ]³⁺, [ Cr ( H ₂ O )₆ ]²⁺, [ Fe ( H ₂ O )₆ ]³⁺, [ Ni ( H ₂ O )₆ ]³⁺, [ Cu ( H ₂ O )₆ ]²⁺ ) [Given atomic numbers : ( V =23, Cr =24, Fe =26, Ni =28 Cu =29 )]

Step-by-step solution

aligned & [ V ( H ₂ O )₆ ]³⁺ d ^2 sp ^3 & ₂₃ ~V :-[ Ar ] 3 ~d ^3 4 ~s ^2 & . ~V ⁺³:-[ Ar ] 3 ~d ^2, n =2 (even number of unpaired e ⁻ ) & [ Cr ( H ₂ O )₆ ]²⁺ sp ^3 ~d ^2 & ₂₄ Cr :-[ Ar ] 3 ~d ^5 4 ~s ^1 & . Cr ⁺²:-[ Ar ] 3 ~d ^4, n =4 (even number of unpaired e ⁻ ) aligned aligned & [ Fe ( H ₂ O )₆ ]³⁺ sp ^3 ~d ^2 & Fe ³⁺:-[ Ar ] 3 ~d ^5 4 ~s ^0 & n =5 ( odd number of unpaired e ⁻ ) & [ Ni ( H ₂ O )₆ ]³⁺ sp ^3 ~d ^2 & Ni :-[ Ar ] 3 ~d ^8 4 ~s ^2 & . Ni ⁺³:-[ Ar ] 3 ~d ^7, n =3 (odd number of unpaired e ⁻ ) & [ Cu (