What is the hybridisation of the oxygen atom in water?

Concept:

Hybridization:

• The atomic orbitals s, p, d, f of the central atom having compatible energies mix up.

• This leads to the formation of new hybrid orbitals which have now different energies, shapes, and orientations than the component atomic orbitals.
• The number of hybrid orbitals is equal to atomic orbitals mixing.
•  After the formation of hybrid orbitals, they overlap with atomic orbitals of suitable side atoms and leads to the formation of covalent chemical bonds.
• The formula for calculating hybridization - H = ½ ( V + M -C + A )
• Where V = number of valence electrons on the central atom. M = No. Of monovalent atoms C = cationic charge A = anionic charge.

Few types of hybridization, their modes of mixing, and geometry of molecules are-

Explanation:

H2O:

• Oxygen is the central molecule.
• Oxygen donates six electrons towards hybridization and one electron is donated by each hydrogen atom.
• So total number of electrons = 2 + 6 = 8 and number of pairs = 4. Hence, H = 4 and the hybridisation is sp³. 
• Out of four pairs, two are bond pairs and two are lone pairs.
• The expected geometry is tetrahedral but the actual shape is bent.

Hence, the hybridization of the oxygen atom in water is sp³.

Additional Information

• Due to the presence of lone electrons, there is repulsion between bond pairs and lone pairs.
• The repulsion between l.p is > b.p and thus pushes the two bonds to come closer decreasing the bond angle from ideal 109.8°.