Covalent Bond

Chemistry

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Formation of covalent compounds

Covalent compounds are formed by sharing of electrons. The sharing results in completion of octet so the species become stable. e.g Oxygen has six electrons in the outermost shell. It needs two electrons to complete the octet. Oxygen shares two electrons with another oxygen atom to complete the octet.

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Covalent bond

Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to attain the nearest noble gas configuration.

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Formation of Hydrogen molecule

Each H atom has one valence electron. When two H atoms react, they share a pair of electrons. In the sharing of a pair of electrons, a chemical bond is formed and each hydrogen atom achieves the nearest noble gas configuration of helium. Because the bond involves sharing of electrons, it is called a covalent bond.

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Factors influencing covalent bond

Factors favouring covalent bond are similar electronegativity and high ionisation energy. 

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Chlorine molecule

Two chlorine atoms could both achieve stable inert gas configuration of argon by sharing their single unpaired electron and attain eight electrons in the outermost shell. The two chlorine atoms are said to be joined by a covalent bond. 

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Oxygen molecule

Each oxygen atom has six valence electrons, and is two electrons short of nearest noble gas configuration of neon. Two oxygen atoms can both achieve stable structures by sharing it's electron pair to achieve the nearest noble gas configuration. It forms a covalent bond, as their electro-negativities are equal. Oxygen molecule has double covalent bond.

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Nitrogen molecule

The electronic configuration of nitrogen is 2,5. It needs 3 more electrons to attain the octet of electrons. It shares these 3 valence electrons with another nitrogen atom forming a triple covalent bond.

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Water

Water molecules contain two hydrogen atoms bonded to one oxygen atom. Oxygen, with six valence electrons, needs two additional electrons to complete its valence shell. Each hydrogen contains one electron. Thus, oxygen shares the electrons with two hydrogen atoms to complete its own valence shell, and in return, shares two of its own electrons with each hydrogen, completing the valence shell of hydrogen atoms.

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Covalency

Two atoms combine together to fill the octet. For example, oxygen atoms combine to form an oxygen molecule. The electronic configuration of oxygen is 2, 6. It needs two electrons to complete the octet. So it shares two electrons with the other atom so that they both have completely filled valence shells.

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Formation of covalent bond

When two atoms share electron mutually, they are said to be joined by a covalent bond. Covalent bond is of three types: single bond, double bond and triple bond.