2.26 Identify valence and core electrons.

How do you identify valence electrons in an atom?

Valence Electrons:

• Electrons in the outermost energy level (highest principal quantum number, n).

• These electrons are involved in chemical bonding and reactions.

• For example, in Sodium (Na) with the electron configuration 1s2 2s2 2p6 3s1, the valence electron is the one in the 3s1 orbital.

• In Chlorine (Cl) with the configuration 1s2 2s2 2p6 3s2 3p5 the valence electrons are the 7 electrons in the 3s2 3p5 orbitals.

How do you identify core electrons in an atom?

Core Electrons:

• Electrons in the inner energy levels, not involved in bonding.

• These electrons are located in completely filled orbitals and do not participate in chemical reactions.

• For example, in Neon (Ne) with the electron configuration 1s2 2s2 2p6, all the electrons are core electrons because it's a noble gas and doesn't have any unfilled outer orbitals.

.

.

.

.