Question

During the formation of a chemical bond
A.Electron-electron repulsion becomes more than nucleus-electron attraction
B.Energy of the system does not change
C.Energy increases
D.Energy decreases

Answer 1

In thermodynamics, we study about the different chemical bonds. The bonding is observed in terms of energy, attraction and repulsion due to presence of electrons, lone pairs and other significant terms. We need to remember that the term chemical bond itself means the attractive force which holds various constituents together in different chemical species.

Complete step by step answer:
We must need to know that the bond energy is measure of bond strength. It helps us to understand how the atoms in the bonding will behave. It is determined by measuring the heat required to break one mole of molecules into in respective atoms. The higher the bond energy, the stronger the bonding is between two atoms.
We must know that when the formation of chemical bonds takes place, the reaction is an exothermic reaction which releases a lot of energy. The electrons involved in the reaction are attracted to the space between nuclei where the electrostatic force of attraction is greater. As the potential energy of electrons decreases, the mechanical energy of the system also decreases. In this process, a lot of energy is lost (reason for exothermic reaction).
Hence, the correct answer to the question is option D.

Note:
We need to know that every atom of different elements has their distinct potential energy. When formation of bond takes place between two respective atoms, due to the reaction taking place the potential energy of the atoms is lost which is converted into mechanical energy in the form of heat and light. This heat or light energy is released after the formation of the bond as a part of the product. Atoms that form strong bonding have low potential energy and those forming weak bonds have high potential energy.