valence shell

The valence shell is the outermost layer of electrons surrounding an atom. These electrons are crucial because they determine how the atom behaves chemically, including how it bonds with other atoms to form molecules. Atoms with a full valence shell are generally stable and less reactive, while those with incomplete shells tend to seek out other atoms to bond with, allowing them to achieve stability. Understanding the valence shell helps explain why certain elements react differently and how they interact in chemical reactions.