Which electrons are most involved in chemical bonding?

The electrons most involved in chemical bonding are the valence electrons. These are the electrons located in the outermost shell of an atom, known as the valence shell.123

Because valence electrons are the least tightly bound to the positive atomic nucleus, they are more weakly attracted than inner-shell electrons. This allows them to be shared between atoms in covalent bonds or transferred from one atom to another to form ionic bonds.12

The behavior of these electrons is fundamental to chemical reactivity, as atoms tend to gain, lose, or share valence electrons to achieve a stable, complete outer-shell configuration—often resembling the eight-electron arrangement of noble gases, a principle known as the octet rule. Conversely, electrons in the inner shells are held much more strongly by the nucleus, making them unavailable for typical chemical reactions.425