Valence Electrons

- valence electrons are all electrons EXCEPT those in the core or in the filled d- or f- subshells

Valence Electrons: in the outermost (energy level) open electron shell of an atom
Open Shell: contains less than its maximum number of electrons
Closed Shell: exactly its maximum number of electrons

ex. Br:  [Ar]4s²3d¹⁰4p⁵  =  7 valence electrons

Ca: [Ar]4s2  =  2 valence electrons

Xe: [Xe]  =  8 valence electrons