Final answer:
Valence electrons are the outer-shell electrons of an atom that determine its reactivity and can participate in chemical bonding, while core electrons are the inner electrons that do not typically engage in bonding. The periodic table can help identify an element's valence electrons, which influence chemical bonding and stability.
Step-by-step explanation:
Valence and core electrons are essential concepts in understanding the chemical behavior of elements. Valence electrons are the electrons in the outermost shell of an atom, which largely control the atom's chemistry and its ability to participate in the formation of chemical bonds. These electrons determine the atom's reactivity, as they are the ones that interact with other atoms during chemical reactions.
In contrast, core electrons are the electrons in energy levels that are not the outermost level, or in other words, all the electrons that an atom has except for the valence electrons. Those are located closer to the nucleus and do not typically participate in bonding. Core electrons can also shield valence electrons from the nuclear charge.
When determining the valence electrons for an element, you can use the periodic table, as elements in the same column (group) have the same valence electron configuration. The number of valence electrons also influences how atoms bond with each other and achieve stable electronic configurations, often following the octet rule where atoms tend to have eight electrons in their valence shell.