Silicon (Si) is in group 14 of the periodic table, meaning it has 4 valence electrons. To achieve a stable octet, it needs to gain 4 more electrons.

Chlorine (Cl) is in group 17, meaning it has 7 valence electrons and needs to gain 1 electron to achieve a stable octet.

Therefore, one silicon atom needs four chlorine atoms to form a stable compound, SiCl₄ (silicon tetrachloride). Each chlorine atom will share one electron with the silicon atom, forming a single covalent bond. This results in the silicon atom having a full octet of electrons, and each chlorine atom also having a full octet.