Question

Which compound in each of the following pairs has the larger lattice energy? Note: Mg₂+ and Li+ have similar radii; O₂– and F– have similar radii. Explain your choices.

(a) MgO or MgSe
(b) LiF or MgO
(c) Li₂O or LiCl
(d) Li₂Se or MgO

Answer 1

The lattice energy of an ionic compound is higher when the compound consists of ions with higher charges and smaller radii, because these factors lead to a stronger electrostatic attraction between the ions.

Step-by-step explanation:

Lattice energy is the energy released when ions are combined to form a compound. It is influenced by the charge of the ions and their radii. A higher charge and smaller ionic radii generally lead to a larger lattice energy.

• (a) MgO has larger lattice energy than MgSe because O has a smaller radius than Se and they both have -2 charge.
• (b) MgO has a larger lattice energy than LiF because Mg+ has a higher charge than Li+.
• (c) Li2O has a larger lattice energy than LiCl because O has a -2 charge, which is higher than the -1 charge of Cl.
• (d) MgO has a larger lattice energy than Li2Se because both Mg+ and O have higher charges than Li+ and Se.

The lattice energy is higher for ionic compounds with ions that have higher charges and smaller radii, which leads to strong electrostatic attraction between the ions, thus requiring more energy to separate them.