Question

How do you determine the molecule is linear?

Answer 1

Hint If the hybridisation of the central atom in a molecule is $\text{s}{{\text{p}}^{\text{2}}}$ then the shape of the molecule is trigonal planar and the hybridization of the central atom is $\text{s}{{\text{p}}^{\text{3}}}$ then the shape of the molecules will be tetrahedral.
In tetrahedral arrangement, the bond pairs lie at an angle of ${{109}^{\circ }}$ while in square arrangement the bond pairs are arranged at an angle of ${{90}^{\circ }}$ .

Complete Step by step solution:
- In the question it is given that how to determine the shape of the given molecule is linear.
- We know that the geometry of a molecule is going to be determined by the bond angle which is present in between the bond pairs and the hybridization of the central ion.
- Hybridization is defined as an intermixing of a set of atomic orbitals of slightly different energies, there by forming a new set of orbitals having equivalent energies and shapes. These hybrid orbitals have minimum repulsion in between their electron pairs and thus are more stable. Hybridization helps indicate the geometry of the molecule.
- For example if the central atom of a molecule $\text{(for e}\text{.g}\text{. BC}{{\text{l}}_{3}})$ is $\text{s}{{\text{p}}^{\text{2}}}$ hybridised then the shape will be trigonal planar, and if the central atom of a molecule is $\text{sp}$ hybridized then the shape of the molecule $\text{( for e}\text{.g}\text{. C}{{\text{O}}_{\text{2}}})$ will be linear.
- According to valence bond theory, the electron pairs around the central atom lie as far as possible so that the repulsive interaction between them should be minimum. For e.g. in the case of $\text{C}{{\text{H}}_{\text{4}}}$ the bond angle between the bond pairs is ${{90}^{\circ }}$ the shape of the molecule will be square planer while if the bond angle in between the bond pair is ${{109}^{\circ }}{{28}^{'}}$ the shape of the molecule will be tetrahedral.
- If a molecule has only two bond pairs and the bond angle is ${{180}^{\circ }}$ then the shape of the molecule will be linear.

Note: $\text{BeC}{{\text{l}}_{\text{2}}}$ has linear structure, hence its bond angle is ${{180}^{\circ }}$ . If a molecule have three lone pair, two bond pair and central atom is $\text{s}{{\text{p}}^{3}}\text{d}$ hybridised then the molecule will have linear geometry.