Match List-I (ligand) with List-II (type of ligand).List-IList-II(a)…

The correct answer is Option (4) → (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

Ligands are classed by the number of donor atoms that bind the metal ion and by how they bind. Monodentate and bidentate are the same as the terms unidentate and didentate.

(a) NH₃ — This matches (iv) Monodentate ligand. It binds through its single nitrogen donor atom.

(b) NO₂⁻ — This matches (iii) Ambidentate ligand. The nitrite ion can bind either through nitrogen (–NO₂) or through oxygen (–ONO).

(c) en — This matches (ii) Bidentate ligand. Ethane-1,2-diamine, \( \ce{H2NCH2CH2NH2} \), binds through its two nitrogen atoms.

(d) EDTA — This matches (i) Chelating ligand. EDTA⁴⁻ is hexadentate: it binds one metal ion through two nitrogen and four oxygen atoms at the same time, forming a chelate. (en also forms chelates, but it is the only bidentate ligand in the list, so it takes (ii).)

NCERT (2026-27 edition):
5.2 Definitions of Some Important Terms Pertaining to Coordination Compounds – “When a ligand is bound to a metal ion through a single donor atom, as with Cl^–, H₂O or NH₃, the ligand is said to be unidentate. When a ligand can bind through two donor atoms as in H₂NCH₂CH₂NH₂ (ethane-1,2-diamine) or C₂O₄^2– (oxalate), the ligand is said to be didentate … Ethylenediaminetetraacetate ion (EDTA^4–) is an important hexadentate ligand. It can bind through two nitrogen and four oxygen atoms to a central metal ion.”

“When a di- or polydentate ligand uses its two or more donor atoms simultaneously to bind a single metal ion, it is said to be a chelate ligand. … Ligand which has two different donor atoms and either of the two ligetes in the complex is called ambidentate ligand. Examples of such ligands are the NO₂^– and SCN^– ions.”