Two atoms have the electron configurations 1s2 2s2 sp6 and 1s2 2s2 2p6 3s1. The first ionization energy of one is 2080 kJ/mol and that of the other is 496 kJ/mol Match each ionization energy with one of the given electron configurations. Justify your choice.

The element with the configuration 1s², 2s², 2p⁶, 3s¹ has the ionization energy of 496 kJ/mol. This is because this element has only one electron in its third shell, meaning it will release its electron quickly to attain stable configuration, causing its first ionization energy to be low.