What is the definition of the term first ionization energy?

A.     The energy released when one mole of electrons is removed from one mole of gaseous atoms.

B.     The energy required to remove one mole of electrons from one mole of gaseous atoms.

C.     The energy released when one mole of gaseous atoms gains one mole of electrons.

D.     The energy required to add one mole of electrons to one mole of gaseous atoms.

B