* Electronegativity: Aluminum (Al) is less electronegative than nitrogen (N). Electronegativity is the ability of an atom to attract electrons in a chemical bond. The less electronegative element is typically written first in a chemical formula.
* Cation and Anion: Aluminum tends to form a +3 cation (Al³⁺) while nitrogen forms a -3 anion (N³⁻). The positive ion (cation) is written first in the formula, followed by the negative ion (anion).
* Chemical Bonding: Aluminum nitride is an ionic compound. The bond is formed by the electrostatic attraction between the positively charged aluminum ions and the negatively charged nitrogen ions. This further reinforces the convention of writing the cation first.
Therefore, the correct formula for aluminum nitride is AlN, reflecting the relative electronegativity of the elements and the formation of a cation (Al³⁺) and an anion (N³⁻).
