A covalent bond is a chemical bond that involves sharing of pairs of electronsbetween atoms. These pairs of electrons are known as bonding pairs or shared pair.
Covalent bond is also known as molecular bond. Covalent bonding arises between two atoms of the same element, or of elements which are close to each other in the periodic table. Covalent bonding occurs primarily between non-metals; but, it can also be witnessed between metals and non-metals. Covalent bonds are most likely to occur, when atoms have similar electro negativities.
History of covalence
The term covalence was first used in 1919 in regards to bonding, by Irving Langmuir in article of “Journal of the American Chemical Society”, titled "The Arrangement of Electrons in Atoms and Molecules".
However, the idea of covalent bonding could be traced to Gilbert N. Lewis, numeral years before 1919, who in 1916 explained the sharing of electron pairs between atoms.
What are various types of covalent bonds?
There exist three types of covalent bonds which is based upon number of shared electron pairs.
Single covalent bond: Single covalent bonds between two atoms are formed, when there exist a mutual sharing of one electron pair. Single covalent bond is denoted by short single line (----).
Double covalent bond: Single covalent bonds between two atoms are formed when there exist mutual sharing of two electron pairs. Double covalent bond is denoted by short double line (=).
Triple covalent bond: Triple covalent bond is formed, when there is sharing of three electron pairs. This bond is denoted by triple short line.
Polar covalent bond: When a covalent bond is formed between two different atoms, it is said as polar covalent bond.
Non-polar covalent bond: When a covalent bond is formed between two like atoms, it is said as non-polar covalent bond.
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