valency
noun [ C ] uk/ˈveɪ.lən.si/ us/ˈveɪ.lən.si/ (also valence, /ˈveɪ.ləns/ /ˈveɪ.ləns/)
chemistry specialized价，原子价，化合价
a measurement that shows the number of hydrogen atoms that can combine with one atom of a particular chemical element to make a compound, used to describe how easily an element can connect in a chemical way with others
Zinc has a valency of 2. 锌是二价元素。
His theory was that carbon had a combining power (valency) of four or two and a unique capacity for joining itself to other atoms of its own kind.
Sodium is useful in a great many compounds as a substitute for one of the two atoms of hydrogen (also valence 1) in a variety of acids.