Answer:
Ionic compound
Step-by-step explanation:
Aluminium fluoride is considered as ionic compound because of large electronegativity difference between bonded atoms.
Ionic bond:
It is the bond which is formed by the transfer of electron from one atom to the atom of another element.
Both bonded atoms have very large electronegativity difference. The atom with large electronegativity value accept the electron from other with smaller value of electronegativity.
For example:
Aluminium fluoride is ionic compound. The electronegativity of fluorine is 3.98 and for aluminium is 1.61. There is large difference is present. That's why electrons from aluminium are transfer to the fluorine. Aluminium becomes positive and fluorine becomes negative ion. Both atoms are bonded together electrostatic attraction occur between anion and cations.
The oxidation state of aluminium is +3 because it can lose three of its valance electrons and form cation and stable electronic configuration while that of fluorine is -1 that's why three fluorine atoms are attached with one atom of Al to make compound neutral.
Al + 3F → AlF₃