Here's why:

* Electron Configuration: Silicon has an electron configuration of [Ne] 3s² 3p². It has four electrons in its outer shell, which is the valence shell.

* Octet Rule: To achieve a stable electron configuration (like the noble gases), silicon needs to gain four more electrons. It does this by sharing its four valence electrons with other atoms, forming four covalent bonds.

* Example: In silicon dioxide (SiO₂), each silicon atom forms four covalent bonds with two oxygen atoms.