Here's why:

* Electron Configuration: Boron has an electron configuration of 2s²2p¹, meaning it has three valence electrons.

* Octet Rule: Boron strives to achieve a stable octet configuration by having eight electrons in its outermost shell. To do this, it needs to gain five more electrons.

* Covalent Bonding: Boron achieves this stability by sharing its three valence electrons with three other atoms, forming three covalent bonds.

Example: In boron trifluoride (BF₃), boron forms three covalent bonds with three fluorine atoms.