Charles Augustine Coulomb

The first measurements of the force of attraction between oppositely charged particles were reported by Charles Augustine Coulomb between 1785 and 1791. Coulomb found that the force of attraction was directly proportional to the product of the charges on the two objects (q₁ and q₂) and inversely proportional to the square of the distance between the objects (r²).

The strength of the bond between the ions of opposite charge in an ionic compound therefore depends on the charges on the ions and the distance between the centers of the ions when they pack to form a crystal.