it converts into a bigger energy level
It's valence shell (outermost shell of atom) is full and stable.
Atoms can fill their outermost energy level by either gaining electrons from other atoms or by sharing the outermost electrons with another atom.
When atoms combine to form molecules, they can gain, lose, or share electrons in order to achieve a stable electron configuration. This process allows atoms to fill their outermost electron shell and attain a more stable, lower energy state.
The combination of the atoms releases heat energy.
When carbon and oxygen atoms combine to form carbon dioxide, energy is released. This energy comes from the bonds being formed between the atoms during the chemical reaction.
Molecules.
Noble gases does not easily combine with other elementsbecause they are stable and have complete outermost shell.
Valence
They OVERLAP
The conditions meet the criteria of atomic combination.
They change
Atoms can combine only if they are having an incomplete valence shell. They combine to attain an octet structure. They can also share electrons. There are some elements whose atoms do not combine, they are the inert gases.