Question

Discuss the structure of H₂O molecule.

Answer 1

1. The core group of 16 atoms in the ground state undergoes sp³ hybridisation to generate all of these angular-shaped hydrides. For example, one 2s and three 2p atomic orbitals of the ground state of the oxygen atom \[\ce{(1s^2 2s^2 2p^2_x 2p^1_y 2p^1_x)}\] mix up and redistribute their energies to form four sp3 hybrid orbitals that are orientated towards the four corners of a regular tetrahedron at an angle of 109°28' during the formation of the H₂O molecule.
2. Two \[\ce{O - H}\] σ-bonds are formed when the two half-filled sp³ hybrid orbitals overlap with the s atomic orbitals of two hydrogen atoms; the other two sp³ hybrid orbitals, each of which carries a single pair of electrons, do not form a bond. Thus, an angled H₂O molecule is produced.
3. Two lone pairs and two bond pairs of electrons encircle the oxygen atom in the H₂O molecule. The expected \[\ce{H - O - H}\] angle of 109°28' decreases to 104.5°, the observed \[\ce{H - O - H}\] angle in H₂O, because the lone pair-bond pair repulsion is stronger than the bond pair-bond pair repulsion.
4. The figure shows the structure of H₂O. The other hydrides of the group possess similar structures and are formed in the same way as discussed above for H₂O.