valence


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valence

 [va´lens]
1. a positive number that represents the combining power of an element in a chemical compound, i.e., the number of bonds each atom of that element makes with other atoms. In this most general sense “valence” has been superseded by the concept “oxidation number.” However, “valence” is still used to indicate (1) the number of covalent bonds formed by an atom in a covalent compound or (2) the charge on a monatomic or polyatomic molecule.
2. in immunology, the number of antigen binding sites possessed by an antibody molecule, two per immunoglobulin monomer, or the number of antigenic determinants possessed by an antigen, usually a large number.

va·lence

, valency (vā'lĕns, -len-sē),
The combining power of one atom of an element (or a radical), that of the hydrogen atom being the unit of comparison, determined by the number of electrons in the outer shell of the atom (v. electrons); for example, in HCl, chlorine is monovalent; in H2O, oxygen is bivalent; in NH3, nitrogen is trivalent.
[L. valentia, strength]

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.

valence

(vā′ləns) also

valency

(-lən-sē)
n. pl. val·lences also val·lencies
1. Chemistry
a. The combining capacity of an atom or group of atoms as determined by the number of electrons it can lose, add, or share when it reacts with other atoms or groups. Also called oxidation state.
b. An integer used to represent this capacity, which may be given as positive or negative depending on whether electrons are lost or gained, respectively: The valences of copper are +1 and +2.
2. The number of binding sites of a molecule, such as an antibody or antigen.
3. The number of different antigens contained in a vaccine, corresponding to the number of pathogens that it is active against.
4. Psychology The degree of attraction or aversion that an individual feels toward a specific object or event.

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.

va·lence

, valency (vā'lĕns, -ē)
The combining power of one atom of an element (or a radical), that of the hydrogen atom being the unit of comparison, determined by the number of electrons in the outer shell of the atom (v. electrons); e.g., in HCl, chlorine is monovalent; in H2O, oxygen is bivalent; in NH3, nitrogen is trivalent.
[L. valentia, strength]

va·lence

, valency (vā'lĕns, -sē)
The combining power of one atom of an element (or a radical), that of the hydrogen atom being the unit of comparison, determined by the number of electrons in the outer shell of the atom (v. electrons).
[L. valentia, strength]

valence (vā´ləns),

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.

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.
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