noun
Chemistry term for the combining power of an element, measured by the number of hydrogen atoms it can displace or combine with.
炭素の原子価は4です。
The valence of carbon is 4.
原子価を理解すると化学反応がわかりやすくなる。
Understanding valency makes chemical reactions easier to grasp.
Compound of 原子 (atom) and 価 (value, worth), a calque from Western chemistry terminology.