Co-ordination Compounds MCQs for NEET — Chemistry Questions with Answers

A ligand is a Lewis base because it donates a pair of electrons to the central metal atom or ion to form a coordinate covalent bond.

The coordination number of a complex is defined as the number of unidentate ligands directly bonded to the central metal ion. For example, in the complex ion ext{[Co(NH}_3 ext{)}_6 ext{]}^{3+}, the coordination number of cobalt is 6 because it is bonded to six ammonia molecules.

Tetrahedral complexes have a coordination number of 4. This is because the central metal ion in such complexes is surrounded by four ligands. For instance, in the tetrahedral complex ext{[Ni(CO}_4 ext{]}, the nickel ion is coordinated to four carbon monoxide ligands.

The compound ext{[Fe(CO}_5 ext{]} has the lowest oxidation state of iron, which is 0. This is because carbon monoxide is a neutral ligand, and the sum of the oxidation states of the ligands is zero, leading to an overall oxidation state of zero for iron in this complex.

Ethylene diamine (often abbreviated as en) is a bidentate ligand. This means it can form two bonds with a central metal ion, utilizing its two nitrogen atoms, each of which has a lone pair of electrons. This allows it to form chelate rings with the metal ion, increasing the stability of the complex.

The IUPAC name of $[Ni(NH_3)_4][NiCl_4]$ is Tetraammine nickel (II) - Tetrachloridonickelate (II). In this complex, the cationic part is $[Ni(NH_3)_4]^{2+}$ and the anionic part is $[NiCl_4]^{2-}$. When naming such complexes, the name of the cation precedes the name of the anion. Moreover, the anionic complex ends with the suffix '-ate'.