The number of complexes from the following with exactly 3 electrons in their t_ 2g orbitals is [ Cr ( H ₂ O )₆]³⁺, [ Fe ( H ₂ O )₆]³⁺, [ Mn ( CN )₆]⁴⁻, [ CoF ₆]³⁻, [ Ni ( H ₂ O )₆]²⁺

Step-by-step solution

[ Cr ( H ₂ O )₆]³⁺ Cr ³⁺ (d^3) t_ 2g ^3 e_g^0 (3 electrons in t_ 2g ) [ Fe ( H ₂ O )₆]³⁺ Fe ³⁺ (d^5) H ₂ O is a weak field ligand for Fe(III), so high spin t_ 2g ^3 e_g^2 (3 electrons in t_ 2g ) [ Mn ( CN )₆]⁴⁻ Mn ²⁺ (d^5) CN ^- is a strong field ligand, so low spin t_ 2g ^5 e_g^0 (5 electrons in t_ 2g ) [ CoF ₆]³⁻ Co ³⁺ (d^6) F ^- is a weak field ligand, so high spin t_ 2g ^4 e_g^2 (4 electrons in t_ 2g ) [ Ni ( H ₂ O )₆]²⁺ Ni ²⁺ (d^8) t_ 2g ^6 e_g^2 (6 electrons in t_ 2g ) Thus, exactly 2 complexes have 3 electro