Question

What is the structure of Water in the VSEPR Theory?

Answer 1

Step 1: Hybridization:

• “Hybridization is defined as the process of intermixing of the orbitals of slightly different energies so as to redistribute their energies, resulting in the formation of a new set of orbitals of equivalent energies and shape.”

Step 2: Formula used for calculation:

• $\mathrm{Steric}\mathrm{number}=\frac{1}{2}\left[\mathrm{V}+\mathrm{M}-\mathrm{C}+\mathrm{A}\right]$
• Where V is the number of valence electrons on the central atom, M is the monovalent electron, C is the positive charge and A represents the negative charge.

Step 3: Calculation for Hybridisation of ${\mathrm{H}}_2\mathrm{O}$:

• The total number of valence electrons in ${\mathrm{H}}_2\mathrm{O}$ is 6 and there are 2 monovalent atoms.
• $$\begin{gathered} \mathrm{Steric}\mathrm{number}=\frac{1}{2}\left[6+2\right]=\frac{1}{2}\times 8 \\ \mathrm{Steric}\mathrm{number}=4 \end{gathered}$$
• The steric number is 4, thus the hybridization of ${\mathrm{H}}_2\mathrm{O}$ is ${\mathrm{sp}}^3$.

Step 4: Structure and shape of ${\mathrm{H}}_2\mathrm{O}$:

• The total number of electron pairs in the valence shell of the oxygen atom is 2. Its electron pair geometry is Tetrahedral and it has two lone pairs and two bond pairs.
• Therefore, according to the VSEPR theory, water molecules have a bent shape (they are V-shaped).