s-Block Elements — JEE Main · 2021 · 27 Jul 2021 · Shift 1 Question with Solution

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.
Assertion R: Lithium halides are some what covalent is nature.
Reason R: Lithium possess high polarisation capability.
In the light of the above statements, choose the most appropriate answer from the options given below:

(A) $A$ is true but $R$ is false
(B)Both $A$ and $R$ are true but $R$ is NOT the correct explanation of $A$
(C) $A$ is false but $R$ is true
(D)Both $A$ and $R$ are true and $R$ is the correct explanation of $A$ ✓ Correct

Answer: (D)

Solution

Lithium halides do have appreciable covalent character.

L i^{+}

is the smallest cation of the alkali metals, so its positive charge sits in a very small volume and its polarising power is the highest in the group. By Fajans' rules such a cation distorts the electron cloud of the large, easily polarised halide ion and pulls charge density into the region between the two nuclei, and shared electron density between two nuclei is covalent bonding; the effect grows from LiF to LiI as the anion becomes larger and softer. Both the assertion and the reason are true, and the high polarising capability of lithium is precisely the reason for the covalent character of its halides.

JEE Main · 2021 · 27 Jul 2021 · Shift 1 · Single correct option

JEE Main · 2021 · 27 Jul 2021 · Shift 1 · s-Block Elements

Solution

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