Question

Lattice energy depends on:
(A). Only radius of cation
(B). Only radius of anion
(C). Cation to anion radius ratio
(D). Sum of the radii of cation and anion

Answer 1

The lattice energy of a crystalline solid is a measure of the energy released when ions are combined to make a compound. It is a measure of the cohesive forces that bind ions, thus it is evident that it depends on the charge on the ions, and size of the ions.

Complete step by step answer:
Lattice energy is defined as the energy required to separate a mole of an ionic solid into gaseous ions. Lattice energy cannot be measured empirically, but it can be calculated using electrostatics or estimated using the born-haber cycle.
Two main factors that contribute to the magnitude of the lattice energy are the change and radius of the bonded ions.
Exothermic reaction:
A process which releases heat into its surroundings.
Lattice energy:
The amount of energy released upon formation of a crystalline ionic solid from gaseous ions.
This model emphasizes two main factors that contribute to the lattice energy of an ionic solid, the change on the ions, and the radius, or size of the ions. The effect of those factors is:
-As the change of the ions increases, the lattice energy increases.
-🡪 As the size of the ions increases, the lattice energy decreases.

Hence, the correct answer is (D).

Additional Information:-
Lattice energy is extensively used in the evaluation and assessment of electron relations helps and fluoride relationships. It is also used in the calculation of standard enthalpies of formation and to measure the strength of ionic acids.
Lattice energy of a compound depends on a number of factors
🡪 As the changes on the ions increase the lattice energy increases (becomes more negative).
🡪 When ions are closer together the lattice energy increases (becomes more negative ).

Note: As an example, the lattice energy of sodium chloride, $NaCl$, is the energy released when gaseous $N{a^ + }$ and $C{l^ - }$ ions come together to form a lattice of alternating ions in the $NaCl$ crystal.