Answer 1

i. Strong field ligands: Those ligands which cause larger splitting of d orbitals and favour pairing of electrons are called strong field ligands. Strong field ligands contain C, N, and P as donor atoms.

e.g. CN^– , NCS^– , CO, NH₃, EDTA, en (ethylenediammine).

ii. Weak field ligands: Those ligands which cause lower splitting of d orbitals i.e., ∆_° parameter is smaller compared to the energy required for the pairing of electrons are called weak field ligands. Weak field ligands contain halogen, O, and S as donor atoms.

e.g. F^– , Cl^– , Br^– , I^–, SCN^–, `"C"_2"O"_4^{2-}`.