Here's why:
* Calcium (Ca) is a metal and tends to lose two electrons to form a +2 cation (Ca²⁺).
* Nitrogen (N) is a nonmetal and tends to gain three electrons to form a -3 anion (N³⁻).
To achieve electrical neutrality in the compound, three calcium ions (3 x +2 = +6) combine with two nitrogen ions (2 x -3 = -6).
The strong electrostatic attraction between the positively charged calcium ions and the negatively charged nitrogen ions is what constitutes the ionic bond.
