Ionic bonds form as a result of the electrostatic attraction between

Ions

Explanation:

Ionic bonds are formed when an element loses electrons (usually a metal), and other elements gain these electrons(usually a nonmetal or the hydrogen). When the element loses electrons, it becomes a cation, an ion with a positive charge; and when the element gains electrons it becomes an anion, an ion with a negative charge.

The charge in the ions produces an electrostatic attraction between them, and that attraction is the force that gets them together in a bond.

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)

you need to have a picture of the atom that way we can answer it