Electron affinity is defined as the energy released when _______________.
1) 1 mole of electrons is completely removed from 1 mole of gaseous atoms/ions.
2) 1 mole of electrons is completely removed from 1 mole of solid atoms/ions.
3) 1 mole of electrons is added to 1 mole of gaseous atoms/ions.
4) 1 mole of electrons is added to 1 mole of solid atoms/ions.