Covalent bond is formed due to mutual sharing of electrons by the combining atoms. The shared pair of electrons lies between the two nuclei. Both the nuclei attract the shared pair of electrons. The shared pair of electrons thus keeps them together, and a stable bond is formed.
A covalent bond may be defined as follows: A covalent bond is defined as the force of attraction between the two combining atoms due to mutual sharing of electrons.
The covalent bond formed due to the sharing of one pair of electrons is represented by a single dash (-) between the two atoms. For example, two hydrogen atoms when combine by mutual sharing, share one pair of electrons between them. So, the covalent bond formed between the two hydrogen atoms (H) is shown as a dash (-) viz.
Single, double and triple covalent bonds
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Covalent bonds are formed due to mutual sharing of electrons. Depending upon the nature of combining atoms, one or more than one shared pairs of electrons may be shared by the two combining atoms. Accordingly, different types of covalent bonds are formed. These are described below:
1. Single covalent bond:
A covalent bond formed by mutual sharing of one pair of electrons is called single covalent bond, or simply as a single bond. A single bond is denoted by a single dash (-) between the two atoms. For example, the two hydrogen atoms in H2 molecules are bonded by a single bond, because two H atoms share only one pair of electrons. Due to mutual sharing of electrons each hydrogen atom acquires stable electronic configuration of helium (the nearest noble gas).
2. Double covalent bond:
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The covalent bond formed by mutual sharing of two pair of electrons between the two atoms is termed as double covalent bond or simply as double bond. This is denoted by a set of two dashes (=). For example, two oxygen atoms combine together to form a molecule of oxygen by mutual sharing of two pair of electrons.
Due to mutual sharing of two pair of electrons, each oxygen atom acquires stable electronic configuration of neon (the nearest noble gas)
3. Triple covalent bond:
The bond formed by the mutual sharing of three pair of electrons between the combining atoms is termed as triple covalent bond or simply as triple bond. This is denoted by a set of three dashes (≡). For example, two nitrogen atoms share three pair of electrons to form a molecule of Nitrogen (N2). Thus, in nitrogen molecule, the two nitrogen atoms are bonded to each other by a triple bond. Due to mutual sharing, both the nitrogen atoms acquire a stable configuration of neon.