Question -
Answer -
Let us assume that two hydrogen atoms (A andB) with nuclei (NA and NB) and electrons (eA and eB) are taken to undergo areaction to form a hydrogen molecule.
When A and B are at alarge distance, there is no interaction between them. As they begin to approacheach other, the attractive and repulsive forces start operating.
Attractive force arisesbetween:
(a) Nucleus of one atom and its own electroni.e., NA – eA and NB – eB.
(b) Nucleus of one atom and electron ofanother atom i.e., NA – eB and NB – eA.
Repulsive force arisesbetween:
(a) Electrons of two atoms i.e., eA – eB.
(b) Nuclei of two atoms i.e., NA – NB.
The force of attractionbrings the two atoms together, whereas the force of repulsion tends to pushthem apart.
Themagnitude of the attractive forces is more than that of the repulsive forces.Hence, the two atoms approach each other. As a result, the potential energydecreases. Finally, a state is reached when the attractive forces balance therepulsive forces and the system acquires minimum energy. This leads to theformation of a dihydrogen molecule.