Due to strong ligand, this is inner orbital complex and the hybridisation of Fe is d²sp³.

Since, F^- ion is a weak ligand hence, pairing of electrons does not occur and outer orbital complex is formed in [CoF₆]^3-.

[Ni(CN)₄]^2- in this, Ni has dsp² hybridisation with square planar geometry and it is diamagnetic.

A magnetic moment of 1.73 BM corresponds to one unpaired electron. Among the given, (a) and (b) are diamagnetic and (c) is paramagnetic with 3 unpaired electrons (3d⁷ configuration).

F^- ion is weak ligand hence, pairing of electrons does not occur and outer orbital complex is formed in [CoF₆]^3-.

The potassium ferrocyanide, K₄ [Fe(CN)₆] due to strong ligand pairing of electrons occur and it has no unpaired electrons.

 In [Co(NH₃)₆]³⁺ due to pairing cobalt configuration and it is diamagnetic.
In [CoF₆]^3- , F^- being weak ligand pairing does not occur and Co³⁺ ion has configuration . It has 4 unpaired electrons.

ln [NiCI₄]^2- , Ni has sp³ hybridisation with 2 unpaired electrons, i.e. paramagnetic.
In [PdCI₄]^2- Pd has dsp² hybridisation and it has no unpaired electrons, i.e. diamagnetic.

Zn and Ni always give outer orbital complexes with coordination number 6.
[Co(NH₃)₆]³⁺ is diamagnetic complex.
[Cr(NH₃)₆]³⁺ is param agnetic with 3d³ configuration.

[Co(NH₃)₆]³⁺ : For this complex action the 6 valance electrons of cobalt will occupy the 3d orbital, whereas the 6 ligands will occupy 3d,4s and 4p orbitals in d²sp³ hybridisation.

[Co(H₂O)₆]³⁺ : This intermixing is based on quantum mechanics. Transition metals may exhibit d²sp³ hybridization where the d orbitals are from the 3d and the s and p orbitals are the 4s and 3d. it acts as strong ligand when metal ion is in +3 oxidation for metals cobalt.

(i) → (p.s), (ii) → (p,s), (iii) → (q,t), (iv) → (q.r)

A → (iii) (b) B → (i) (c) C → (iv) (d) D → (ii)

a) Six empty orbitals (two d, one s and three p) are available, so whether the ligand is weak (H2​O)  the six orbitals hybridize to give six equivalent d2sp3 hybrid orbitals. Hence, in  [Cr(H2​O)6​]3+  ions chromium is in a state of d2sp3 hybridization.

b)  CN is a strong ligand it makes the unpaired electrons of cobalt to pair up and occupies the space.

• The ligands occupy one d orbital, one s orbital and 2 p orbitals. Thus the hybridisation is “dsp2” with “square planar” geometry.
• It has 1 unpaired electron.

c) In [Ni(NH3)6]2+, Ni is in +2 state and has configuration 3d8. In presence of NH3, the 3d electrons do not pair up. The hybridization is sp3d2 forming an outer orbital complex.

 It has been found that the complex has two unpaired electrons.

Statement I [Ni(CN)₄]^2- is square planar and diamagnetic whereas [NiCI₄]^2- is tetrahedral and paramagnetic .
Statement II [Ni(CN)₄]^2- is square planar while [NiCI₄]^2- is tetrahedral.