Q.Explain in brief with one example:

A covalent bond forms when two atoms — typically of similar electronegativity, or with only a small electronegativity difference — SHARE a pair of electrons rather than transferring one outright, with each atom contributing one electron to the shared pair and having an equal claim on it; this shared-pair bond is drawn as a dash (—) and is often called the Lewis-Langmuir covalent bond. Sharing one electron pair gives a single bond (e.g. H–H in H2); sharing two pairs gives a double bond (e.g. one C=O in CO2); and sharing three pairs gives a triple bond (e.g. N≡N in N2, or C≡C in acetylene). A closely related idea is the co-ordinate (dative) covalent bond, in which BOTH electrons of the shared pair are contributed by just ONE of the two bonded atoms rather than one each — valence bond theory (unlike the simple Lewis picture) has no explanation for how such a bond forms, since its core postulate requires each atom to supply one electron. Covalent bonds are generally classified by the geometry of the orbital overlap that forms them: a s …