How many valence electrons does an atom require to have a full shell?

The octet rule states that most atoms strive to have eight electrons in their outermost shell, known as the valence shell, to achieve stability. This configuration is similar to that of the noble gases, which are known for their inertness. While there are exceptions to the octet rule (like hydrogen, which only needs two electrons), eight valence electrons is the most common and significant requirement for a full and stable outer shell. Atoms achieve this full shell by gaining, losing, or sharing electrons through chemical bonding.