• What is valence?

    Vladimir Kulinich
    Vladimir Kulinich
    February 21, 2013
    What is valence?

    Often people hear the word "valency", not fully understanding what it is. So what is valence? Valency is one of the terms used in chemical structure. Valency, in fact, determines the ability of an atom to form chemical bonds. Quantitatively, valency is the number of bonds in which an atom participates.

    What is the valence of an element

    Valency is an indicator of the ability of an atom to attach other atoms, forming chemical bonds with them inside the molecule. The number of bonds of an atom is equal to the number of its unpaired electrons. These bonds are called covalent.

    An unpaired electron is a free electron on the outer shell of an atom, which is connected in pairs with the outer electron of another atom. Each pair of such electrons is called “electron”, and each of the electrons is called valence. So the definition of the word "valency" is the number of electron pairs with which one atom is connected to another atom.

    Valency can be schematically depicted in structural chemical formulas. When it is not needed, use simple formulas where the valence is not specified.

    The maximum valence of chemical elements from one group of the periodic table is equal to the ordinal number of this group. Atoms of the same element can have different valences in different chemical compounds. The polarity of the covalent bonds that are formed is not taken into account. This is why the valence has no sign. Also, the valence cannot be a negative value and be equal to zero.

    The number of divalent oxygen atoms or monovalent hydrogen atoms is considered to be a quantitative measure of a chemical element. But when it is necessary to determine the valence, you can use other elements, the valence of which is reliably known. You can determine the valency of chemical elements by reading our article “How to determine the valence?”.

    Sometimes the concept of "valence" is equated to the concept of "degree of oxidation," but this is not so, although sometimes these figures do coincide.The degree of oxidation is a formal term that refers to the possible charge that an atom would receive if its electron pairs passed on to more electrically negative atoms. Here the degree of oxidation can have some sort of sign and is expressed in units of charge. This term is common in inorganic chemistry, because in inorganic compounds it is hard to judge valence. And vice versa, valence is used in organic chemistry, because the molecular structure has most of the organic compounds.

    Now you know what the valence of chemical elements is!

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