Consider these elements: N, Mg, O, F, Al. a. Write the electron configuration for each element. b. Arrange the elements in order
of decreasing atomic radius. c. Arrangetheelementsinorderofincreasingionizationenergy. d. Use the electron configurations in part a to explain the dif- ferences between your answers to parts b and c.
Atomic radius decreases with increase in nonmetallic character. Looking at the electronic configurations, as effective nuclear charge increases, the atom becomes smaller and the attractive force between the nucleus and the outermost electrons increases. Hence, the radius of the atom decreases and ionization energy increases. Note that the addition of more orbital electrons implies addition of more nuclear charge since the both must exactly balance for the atom to remain electrically neutral. The more the electrons in the outermost shell, the higher the first ionization energy.