Valence electrons are more reactive than core electrons due to their location and energy level in an atom. Valence electrons are found in the outermost energy level or shell of an atom, while core electrons are present in the inner energy levels.
The outermost energy level is farthest from the positively charged nucleus, and it is relatively less shielded by the inner electron shells. As a result, valence electrons experience weaker electrostatic attraction to the nucleus compared to core electrons. This weaker attraction allows valence electrons to be more easily involved in chemical reactions and interactions with other atoms.
Additionally, valence electrons are directly involved in the formation of chemical bonds. Elements tend to react with one another to achieve a stable electron configuration, typically by gaining, losing, or sharing valence electrons. The reactivity of an element depends on the ease with which it can gain or lose valence electrons to achieve a more stable configuration.
In contrast, core electrons are generally not involved in bonding and are more tightly held by the nucleus. They are shielded by the presence of inner electron shells and are less likely to participate in chemical reactions.
Overall, the combination of their location, weaker attraction to the nucleus, and active involvement in bonding makes valence electrons more reactive than core electrons.