valence

valence /va·lence/ (va´lens)

1. a positive number that represents the number of bonds that each atom of an element makes in a chemical compound; now replaced by the concept “oxidation number” but still used to denote (a) the number of covalent bonds formed by an atom in a covalent compound or (b) the charge on a monatomic or polyatomic molecule.

2. in immunology, the number of antigen binding sites possessed by an antibody molecule.

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va·lence (vlns) or va·len·cy (-ln-s)

n.

1. The combining capacity of an atom or radical that is determined by the number of electrons that it will lose, add, or share when it reacts with other atoms.

2. A positive or negative integer used to represent this capacity.

3. The number of components of an antigen molecule to which an antibody molecule can bind.

4. The attraction or aversion that an individual feels toward a specific object or event.

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valence

[vāl′əns]

Etymology: L, valere, to be strong

1 (in chemistry) a numeric expression of the capability of an element to combine chemically with atoms of hydrogen or their equivalent. An element is considered monovalent (or univalent) if each of its atoms can react with only one hydrogen atom or its equivalent, divalent (or bivalent) if each atom can react with two hydrogen or equivalent atoms, trivalent (or tervalent) if each atom can react with three hydrogen atoms, and polyvalent (or multivalent) if each atom can react with many hydrogen atoms.

2 (in immunology) an expression of the number of antigen-binding sites for one molecule of any given antibody or the number of antibody-binding sites for any given antigen. Most antibody molecules, and those belonging to the IgG, IgA, and IgE immunoglobulin classes, have two antigen-binding sites. Most large antigen molecules are multivalent.

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valence (vā´lns),

n 1. in chemistry, a numeric expression of the capability of an element to combine chemically with atoms of hydrogen or their equivalent.
n 2. in immunology, an expression of the number of antigen-binding sites for one molecule of any given antibody or the number of antibody-binding sites for any given antigen.

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valency, valence

1. the numerical measure of the capacity to combine; in chemistry, an expression of the number of atoms of hydrogen (or its equivalent) that one atom of a chemical element can hold in combination, if negative, or displace in a reaction, if positive.

2. in immunology, an expression of the number of antigenic determinants with which one molecule of a given antibody can combine.