Here's why:

* Valence electrons are the electrons in the outermost energy level of an atom. They are the ones furthest from the nucleus and therefore experience the weakest attraction to it.

* Chemical bonds form when atoms share or transfer valence electrons to achieve a stable electron configuration (usually a full outer shell).

* Electrons in inner energy levels are held more tightly to the nucleus and are not involved in bonding.

Let me know if you'd like more details about the different types of chemical bonds!