JEE Main · 2026 · 21 Jan 2026 · Shift 2 · p-Block Elements

Given below are two statements:

Statement I: The correct order in terms of bond dissociation enthalpy is

Cl_{2} > Br_{2} > F_{2} > I_{2}

Statement II: The correct trend in the covalent character of the metal halides is

[SnCl_{4} > SnCl_{2}]

[PbCl_{4} > PbCl_{2}]

and

[UF_{4} > UF_{6}]

In the light of the above statements, choose the correct answer from the options given below:

(A)Statement I is true but Statement II is false✓ Correct
(B)Both Statement I and Statement II are true
(C)Statement I is false but Statement II is true
(D)Both Statement I and Statement II are false

Answer: (A)

Solution

The bond dissociation enthalpies of the dihalogens do not fall monotonically down the group. Fluorine is anomalous: its small size forces the lone pairs on the two bonded atoms very close together, and the resulting lone pair-lone pair repulsion weakens the F-F bond so much that it drops below both Cl-Cl and Br-Br, giving

Cl_{2} > Br_{2} > F_{2} > I_{2}

, so Statement I is correct. For covalent character, Fajans' rules grant greater covalence to the cation of higher charge and smaller size, so

SnCl_{4} > SnCl_{2}

and

PbCl_{4} > PbCl_{2}

are both right, but for the uranium fluorides the higher state

U^{6 +}

gives the more covalent fluoride, making the true order

UF_{6} > UF_{4}

, the reverse of what is written, so Statement II is false. Only the first statement is true.

JEE Main · 2026 · 21 Jan 2026 · Shift 2 · Single correct option

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JEE Main · 2026 · 21 Jan 2026 · Shift 2 · p-Block Elements

Solution

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