What is the term for the outermost electron shell in an atom?

The term "valence shell" refers to the outermost electron shell of an atom. This shell contains the electrons that are involved in chemical bonding and reactions. The valence electrons, which reside in this shell, play a crucial role in determining the chemical properties of an element, including its reactivity, the types of bonds it can form, and its overall behavior in chemical reactions.

Atoms aim to achieve a stable electron configuration, often through gaining, losing, or sharing valence electrons. For instance, elements in the same group of the periodic table have similar valence electron configurations, which contribute to their similar chemical properties. Understanding the concept of the valence shell is essential for studying chemical bonding and molecular interactions.