In chemistry, valency or valence is a measure of an atoms combining capacity with other atoms when it forms chemical compounds or molecules). It is generally understood to be the number of chemical bonds that each atom of a given element typically forms). The valency of an atom is the number of bonds formed by the atom in a specified compound). Double bonds are considered to be two bonds, and triple bonds are considered to be three). In most compounds, the valency of hydrogen is 1, of oxygen is 2, of nitrogen is 3, and of carbon is 4). The valency is the combining capacity of an atom of a given element, determined by the number of hydrogen atoms that it combines with). For example, in methane, carbon has a valency of 4; in ammonia, nitrogen has a valency of 3; in water, oxygen has a valency of 2; and in hydrogen chloride, chlorine has a valency of 1).
Valency is different from the oxidation number, and it has no sign. The valency of an element is a measure of its combining capacity and can be defined as the number of electrons that must be lost or gained by an atom to obtain a stable state. The valency of an element can be found by determining the number of hydrogen atoms which can combine directly or indirectly with one atom of the element.
Valency is an important concept in chemistry as it helps to predict the chemical behavior of elements and their compounds. It is used to determine the formula of a compound and the way in which atoms are arranged in a molecule).
