NEET Practice Questions (MCQs) with Answers & Solutions

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'.

$ [Cr(C_2O_4)_3]^{3-} $ shows optical isomerism. This is because the oxalate ligands (C_2O_4) can form chiral complexes with chromium, leading to non-superimposable mirror images (optical isomers).

The coordination compound $[Cr(NH_3)_6]^{3+} [Co(CN)_6]^{3-}$ is an example of coordination isomerism. Coordination isomerism occurs when there is an interchange of ligands between cationic and anionic entities of different metal ions within the same complex. Here, $[Co(NH_3)_6]^{3+}$ and $[Cr(CN)_6]^{3-}$ can interchange their ligands to form $[Cr(NH_3)_6]^{3+} [Co(CN)_6]^{3-}$.

According to Werner’s theory, primary valencies correspond to the oxidation state of the central metal ion and are ionizable, whereas secondary valencies correspond to the coordination number and are non-ionizable. Thus, primary valencies are ionizable.

The complex formation with $Ni^{2+}$ depends on the nature of the ligands. Chloride ions ($Cl^-$) typically form tetrahedral complexes with $Ni^{2+}$. Cyanide ions ($CN^-$) form square planar complexes due to the strong field effect. Water ($H_2O$) forms octahedral complexes because it is a weak field ligand. Thus, the correct geometrical shapes for the complexes $[NiCl_4]^{2-}$, $[Ni(CN)_4]^{2-}$, and $[Ni(H_2O)_6]^{2+}$ are tetrahedral, square planar, and octahedral respectively.