Valence shell

The outermost occupied electron shell of an atom. Its electrons participate in chemical bonding and largely determine the atom’s chemical properties.

Electron shell: A group of atomic electron states with similar principal quantum number and energy. The valence shell is the outermost occupied member of an atom’s electron shells.
Chemical bond: An attractive interaction that holds atoms or ions together in a chemical substance. Bond formation is the main way valence-shell electrons link atoms.
Periodic table: A tabular arrangement of chemical elements ordered by atomic number and recurring properties. For main-group elements, column patterns reflect recurring valence-shell configurations.
Core electron: An electron in an atom’s inner shells rather than its outermost occupied shell. Core electrons usually participate less directly in ordinary chemical bonding than valence electrons.
Noble gas: An element in group 18 of the periodic table, generally characterized by low chemical reactivity. Their filled valence shells help explain their characteristically low reactivity.
Atomic orbital: A quantum state describing an electron’s spatial distribution and energy in an atom. Orbitals within the outermost shell hold its valence electrons.
Covalent bond: A chemical bond formed when atoms share one or more pairs of electrons. Shared electron pairs commonly come from the atoms’ valence shells.
Periodic trend: A systematic change in an element property across a period or down a group of the periodic table. Shell occupancy and effective nuclear charge help explain these recurring changes.
Valence band: The highest energy band occupied by electrons in a solid at absolute zero. It is a solid-state energy band, not an individual atom’s outermost electron shell.
Valency: The combining capacity of an atom, expressed through the number of bonds it can form or electrons it can transfer or share. Valence-shell electrons provide a basis for many common valency patterns.

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