The first ionization energy of an element is 736 kJ per mole of atoms. An atom of this element in the ground state has a total of how many valence electrons?
A. 1.
B. 2.
C. 3.
D. 4.
E. 5.
736 kJ/mol is the value for Mg. Use the Periodic Table to find Mg. It has 2 valence electrons.