Electrons in the outermost energy level are usually involved in chemical reactions which are called .

Chemical bonding

Explanation:

Outer most shell's electrons are called valence electrons and they are responsible for the formation of chemical bonds either ionic or covalent when atoms react with each other.

Outer most electrons hold immense importance in the type of chemical bonding an atom will go through in the formation of a molecule.

For example, sodium has only one electron in outermost shell so it is very hard for sodium to share electrons and become stable. Therefore, it never goes for covalent bonding but only goes for ionic bonding where it gives off one electron to another atom (say chlorine who has 7 electrons in outermost shell) and in this process sodium chloride is formed and both sodium and chlorine get stable electronic configuration.

Please see picture for better understanding. Therefore, we can say that  Electrons in the outermost energy level are usually involved in chemical reactions which are called chemical bonding or formation of chemical bonds.

Hope it help!

the answer is d (apex) good luck : ))