Why boron does not form `B^(3+)` ion ?

Explanation

Boron has three electrons in their outer shell. Atomic size of boron is very small. Therefore, the sum of first three ionisation enthalpies (i.e., `IE_(1) +IE_(2) + IE_(3)`) is very high. Boron cannot lose these three valence electrons. Hence, boron does not form trivalent cation (`B^(3+)` ion). Thus, it does not form ionic compounds.