Name: Hybridisation in SF₆ Molecule
Uploaded: 2019-07-19
Duration: 2 min 31 s
Description: Understand the bonding present in the case of sulphur hexafluoride. This video illustrates that the hybridisation present in the case of sulphur hexafluoride...

Question

Briefly describe valence bond theory of covalent bond. How can you interpret it in terms of energy consideration?

Accepted Answer

Covalent bonds are formed when two valence orbitals (half-filled) belonging to two different atoms overlap on each other. The electron density in the area between the two bonding atoms increases as a result of this overlapping, thereby increasing the stability of the resulting molecule.

The presence of many unpaired electrons in the valence shell of an atom enables it to form multiple bonds with other atoms. The paired electrons present in the valence shell do not take participate in the formation of chemical bonds as per the valence bond theory.

In terms of energy consideration, we can explain it by using the example of $H_{2}$ formation.Whenever atoms combine to form a molecule ,there is always decrease in the energy. Actually, when two H atoms are far separated, they do not have any force of interaction (attractive or repulsive). As they tend to come closer, two different forces operates:

(a) The nucleus of one H is attracted towards the electrons of the other H atoms & Vice versa. The energy is released in attraction.

(b) The nuclei of the atoms as well as their electrons repel each other. Energy is needed to overcome the force of repulsion. Now in case, if the magnitude of the attractive forces is more than that of the repulsive forces, a stable molecule will be formed. However, if the repulsive forces are more than the attractive forces, then the atoms will not combine. If for example H_A & H_B are two hydrogen atoms & e_A & e_B are their respective electrons, then attractive & repulsive forces may be shown as follows:

The number of new attractive & repulsive forces is same, but the magnitude of attractive forces is more. Thus, when two hydrogen atoms approach each other, the overall potential energy decreases & hence a stable hydrogen molecule is formed.

Briefly describe valence bond theory of covalent bond. How can you interpret it in terms of energy consideration?

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