Which type of electron is involved in bonding?

Valence electrons are the electrons in the outermost shell of an atom and are crucial in the formation of chemical bonds. These electrons determine an atom's ability to interact and bond with other atoms, as they are the electrons that can be shared with other atoms (covalent bonding), transferred between atoms (ionic bonding), or engaged in metallic bonding.

Core electrons, inner-shell electrons, and free electrons do not participate in bonding to the same extent as valence electrons. Core electrons are located in the inner shells and are shielded from participating in chemical reactions. Inner-shell electrons also refer to those that are not involved in bonding due to their proximity to the nucleus. Free electrons typically refer to electrons in conductive materials that can move freely and contribute to electrical conductivity, but they are not involved in bonding in the context of chemical compounds.

Understanding the role of valence electrons in bonding helps in predicting an element's reactivity and the types of bonds it can form, making them fundamental to various chemical reactions and interactions.