In water molecule (H2O), there are two O – H single covalents bonds.
Electron configuration of 8O is 2,6 and 1H is 1.
Oxygen atom needs ‘2’ electrons to attain octet in its valence shell.
Therefore it shares ‘2’ electron with two hydrogen atoms to form water
(H2O) molecule.
The total number of covalent bonds that an atom of an element forms is called its 'covalency'
Bond length or bond distance is the equilibrium distance between the
nuclei of two atoms which form a covalent bond.
It is generally given in nm (nanometer) or A0
(Angstrom unit).
Bond energy or Bond dissociation energy is the energy needed to break
a covalent bond between two atoms of a diatomic covalent compound in
its gaseous state.
1) When a covalent bond is formed between any two atoms, irrespective
of the nature of the atoms, the bond lengths and bond energies are expected
to be the same. This is because any covalent bond between any two atoms
is a result of mere sharing of two identical electrons. But, practically it
was observed that bond lengths and bond energies are not same when the
atoms that form the bond are different. (See table - 3)