valentie

Valentie (valence) is a term used in chemistry to describe the combining power of an atom, i.e., its ability to form chemical bonds with other atoms. In Dutch, valentie corresponds to the English valence or valency. The concept arose to explain why elements bond in characteristic ways and with specific numbers of atoms.

For main-group elements, valence roughly equals the number of electrons in the outer shell that participate in bonding. In simple terms: carbon valence 4, nitrogen 3, oxygen 2, hydrogen and fluorine 1. Some elements can exceed these numbers in certain compounds through expanded octets (for example sulfur in SF6) or by forming multiple bonds. The octet rule guides intuition but is not universal.

Valence should be distinguished from oxidation state, a formal accounting value assigned to atoms in compounds. Valence describes how many bonds an atom tends to form, while oxidation state tracks electron ownership in a given bonding model. Valence electrons—the outer-shell electrons that participate in bonding—are central to the concept and underpin most counting rules.

The valence concept is complemented by theories such as valence bond theory and molecular orbital theory. In less ideal cases, especially with transition metals and hypervalent species, simple valence counts are insufficient. In linguistics, valency (valentie) refers to the number and type of arguments a verb requires, a related but distinct use of the term. The concept originated with chemists like G. N. Lewis, who introduced the octet rule and bonding capacity.