Which pair of elements would be expected to form an ionic bond

Ionic bonds refer to a complete transfer of electrons between atoms to produce 2 oppositively ion charged. In this kind of bond, the metal loses its electron to become a positive charge and vice versa.
There can be a lot of elements that can be combined to produce an ionic bond.
One example is the fluorine and the lithium.
Flourine is an element with a symbol of F and contains the lightest halogen while lithium is an element with symbol of Li, known to become a silver metal.

The answer would be sand and gravel