Valence electron

A valence electron occupies an atom’s outermost electron shell and can participate in chemical bonding. Its arrangement helps determine an element’s chemical properties and reactivity.

Chemical bond: An attraction that holds atoms or ions together through shared or transferred electrons. Valence electrons are the electrons shared or transferred in many chemical bonds.
Atomic orbital: A mathematical description of a region around an atomic nucleus where an electron is likely to be found. Valence electrons occupy orbitals in an atom’s outer shell.
Valence (chemistry): The combining capacity of an atom, commonly expressed through the number of bonds it forms. Valence electrons help determine how many bonds an atom can form.
Valence band: The highest range of electron energy states in a solid that is occupied at absolute zero. Unlike an individual valence electron, this is a collective energy band in a solid.
Lewis structure: A diagram showing valence electrons as dots and covalent bonds as lines around element symbols. Lewis structures make valence-electron participation in bonding visible.
Electron shell: A group of atomic orbitals with the same principal quantum number, organized by energy and distance from the nucleus. The outermost occupied shell defines which electrons are valence electrons.
Oxidation state: A formal charge assigned to an atom under conventions that treat bonds as ionic. Valence-electron accounting helps track electron transfers in reactions.
Valence electron number: The count of valence electrons in an atom or ion under a specified electron-counting convention. A count summarizes how many such electrons an atom has, rather than naming an electron.
Octet rule: A chemical guideline that atoms often gain, lose, or share electrons to reach eight valence electrons. It predicts many bonding patterns from the tendency to fill the outer shell.
Electron configuration: The distribution of an atom’s electrons among its shells, subshells, and orbitals. It shows which electrons occupy the outer shell and can act as valence electrons.

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