Bond is formed if atoms are getting more stable after bond formation and being stable means less energy state so they release energy while bond formation so it is exothermic process

Bond formation refers to the process of atoms coming together to form chemical bonds. These bonds can be classified as either covalent or ionic, depending on the type of atoms involved and their electronegativity difference. The energy change that occurs during bond formation can be either exothermic or endothermic.

Exothermic bond formation:
- Covalent bonds: In covalent bond formation, two atoms share electrons to achieve a more stable electron configuration. This process releases energy, making it exothermic. The shared electrons are attracted to both nuclei, resulting in a lower potential energy and a more stable system. Examples of exothermic covalent bond formations include the formation of hydrogen gas (H2) or chlorine gas (Cl2).

- Ionic bonds: In ionic bond formation, there is a transfer of electrons from one atom to another, resulting in the formation of oppositely charged ions. This process also releases energy and is exothermic. The electrostatic attraction between the positive and negative ions leads to a lower potential energy and increased stability. Examples of exothermic ionic bond formations include the formation of sodium chloride (NaCl) or magnesium oxide (MgO).

Endothermic bond formation:
- Some covalent bonds: While most covalent bond formations are exothermic, there are exceptions. For example, the formation of some covalent bonds can be endothermic. This occurs when the bonding atoms have a large electronegativity difference, resulting in unequal sharing of electrons. This unequal sharing leads to the formation of polar covalent bonds, which require energy input. Examples of endothermic covalent bond formations include the formation of hydrogen fluoride (HF) or ammonia (NH3).

- Breaking existing bonds: Breaking existing bonds requires energy input and is therefore endothermic. This is because energy is needed to overcome the attractive forces between the bonded atoms. Breaking covalent or ionic bonds requires energy input, making it an endothermic process.

In conclusion, bond formation can be exothermic or endothermic depending on the type of bond and the atoms involved. Most covalent and ionic bond formations are exothermic, releasing energy. However, some covalent bonds can be endothermic due to unequal electron sharing, and breaking existing bonds is always endothermic.