Question

lattice energy can be defined as the $delta h^{circ}$ associated with the separation of a solid crystal into gaseous ions. lattice - enthalpies for four compounds are given in the table.

compound	lif	licl	mgcl₂	srcl₂

2 mark for review
which of the following statements about lattice energy is consistent with the information in the table?
a. it increases with the increasing radii of the ions in the compound.
b. it increases with the decreasing radii of the ions in the compound.
c. it increases with the decreasing charge of the ions.
d. it increases with the decreasing electronegativity of the atoms.

Explanation:

Lattice energy is the energy required to separate a solid ionic crystal into its gaseous ions. According to Coulomb's law, lattice - energy ($U$) is directly proportional to the product of the charges of the ions ($q_1$ and $q_2$) and inversely proportional to the distance ($r$) between the ions in the compound. Mathematically, $U=\frac{kq_1q_2}{r}$, where $k$ is a constant. As the radii of the ions decrease, the distance $r$ between them in the ionic compound decreases, and the lattice energy increases.

Answer:

C. It increases with the decreasing radii of the ions in the compound.