Arrange the following compounds in order of increasing lattice energy: NaF, MgO, KCl, CaS.

To determine the order of increasing lattice energy for the compounds NaF, MgO, KCl, and CaS, it is important to consider both the charges of the ions and their ionic radii.

Lattice energy is fundamentally influenced by two main factors: the charge of the ions and the distance between them. Higher charged ions produce greater electrostatic forces, leading to larger lattice energies. Additionally, smaller ionic radii allow ions to get closer together, which also increases the lattice energy.

1. MgO has a high lattice energy due to the presence of Mg²⁺ and O²⁻ ions. The doubly charged ions significantly increase the electrostatic attraction compared to singly charged ions.

2. CaS also features doubly charged ions (Ca²⁺ and S²⁻), similar to MgO, but since calcium is larger than magnesium, the lattice energy for CaS is generally lower than that for MgO, though still high compared to compounds with singly charged ions.

3. NaF combines Na⁺ and F⁻, both of which are singly charged. While sodium is larger than magnesium and calcium, the smaller size of the fluoride ion contributes to a significant lattice energy, making