Final answer:
The electrons furthest away from the nucleus are called valence electrons and are crucial in determining an atom's chemical properties and reactivity.
Step-by-step explanation:
The electrons that are furthest away from the nucleus interact more with the environment and other atoms. These electrons are called valence electrons. The valence electrons are found in the outermost energy level of an atom and play a significant role in the chemical properties and reactivity of the element. Electrons closer to the nucleus are known as core electrons and do not typically participate in chemical reactions. It is important to remember that electrons do not follow rigid orbits but tend to stay within certain regions of space known as electron shells, each associated with a distinct energy level.