Valence

1 : the degree of combining power of an element as shown by the number of atomic weights of a monovalent element (as hydrogen) with which the atomic weight of the element will combine or for which it can be substituted or with which it can be compared
2 a : relative capacity to unite, react, or interact (as with antigens or a biological substrate) b : the degree of attractiveness an individual, activity, or thing possesses as a behavioral goal