The first ionization energy of sodium is 495.9 kJ/mol. The energy change for the reaction
Na(s) → Na+(g) + e– is therefore
◦ 495.9 kJ/mol.
◦ less than 495.9 kJ/mol.
◦ greater than 495.9 kJ/mol.
◦ is equal to the electron affinity of sodium.
◦ is equal to the second ionization energy of sodium.