Question

Which would you expect to have the highest first ionization energy: Mg, Al, Si? Which would have the highest third ionization energy? Justify your answers.

Answer 1

As we go accross the period, the atomic radii decreases and so the attraction of the electrons to the nucleus becomes stronger and stronger. So comparing Al and Si, Si has a smaller atomic radius and therefore has a stronger ionization energy than Al. Mg has the highest, because unlike Si and Al that have 4 electrons and 3 electrons in the outtermost shell, respectively, Mg has two only and to reach the third electron, the valence shell in broke open and then there is a penetration into an inner shell, where there is a greater attractive force between nucleus and electron, the reason why it has the highest ionization energy.

Answer 2

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