Question

How is an ionic bond formed? How is a covalent bond formed?

Answer 1

Ionic bond is formed by transfer of electrons between metals and non-metals
Covalent bond is formed by sharing electrons between non-metals

Explanation:

Ions that have opposite charges will form an ionic bond in such a way that total charge on the compound is 0.
e.g. Na forms `Na^(+)`ion and Cl forms `Cl^(-)`ions to form a stable octet, which is given by the octet rule.
So the compound formed will be `NaCl` as the opposite charges cancel each other to give 0 charge, which is favourable.

Covalent bond can be formed between non-metals having like charges e.g Sulphur and oxygen both have -2 charge on their ions, but `SO_2` is formed by sharing 2 electrons in the outermost shell so that both elements gain a stable octet
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You can find out which type of bond is formed using the difference in electronegativity of the atoms. We have defined the following:

• <0.5 nonpolar bond
• 0.5-2.0 polar bond
• 2.0< ionic bond

The border between these bonds are rough, but give a nice estimate what it probably should be.