Question

Explain the difference between the valence electrons and the covalency of an element.

Answer 1

We have to know that the valence electrons and covalency of an element both are related with bonding of an atom but are completely different terms. Valency is the capability of an electron to lose or gain electrons in pairing, while on the other hand covalency is the electron sharing between two atoms.

Complete step by step answer:
Valence electrons –
We know that, valency of an atom can be defined as the number of valence electrons available in the outermost shell available for bonding. An atom may either donate electrons or accept electrons from another atom to form a stable bond.
Valency may or may not be equal to the number of valence electrons.
Let us consider carbon, this atom has four valence electrons. But it cannot donate or accept four more electrons from another atom. Therefore, it cannot form an ionic bond but it can form covalent bonds by sharing its electron with other atoms such as hydrogen.
If we consider an atom such as hydrogen it has one electron is the outermost shell which can donate its one electron or accept one electron to form an ionic bond.
Covalency of an element –
We need to remember that a covalent bond is defined as sharing of electron pairs between atoms known as shared pairs or bonding pairs. A stable balance of attractive and repulsive forces between atoms when they share electrons.
We must have to know that the covalency depends upon the number of valence electrons.
If we consider carbon, then it has four electrons in the outermost shell. Since it cannot form ionic bonds it forms covalent bonds sharing its electrons with other atoms like hydrogen.

Note:
We need to know that the valency and covalency are both related to valence electrons, but the definition and properties of both are totally different. One can form ionic as well as covalent bonds while other properties are restricted to form only covalent bonds. The valency of an atom can be either positive or negative depending on its electron accepting and electron donating capacity. The covalency is always positive because it involves sharing of electrons from two different atoms.