Problem 2.61 Part C

[Catherine Yang 3G]

Problem 2.61 asks which member of each pair has the smaller first ionization energy, Al or Na.
Why does Na have a smaller first ionization energy than Al ? I thought that Al would have the smaller first ionization energy because it has one more orbital than Na that is farther from the nucleus. Is it because Al has more protons to hold its electrons more closely?

[Harrison Wang 1H]

Yes, ionization energy generally increases from left to right across a period because the electrons are closer to the nucleus from the added protons and higher positive charge

[Kyung_Jin_Kim_1H]

Because Na only has to lose one electron before it becomes more stable and has a valence structure with 8 electrons. Na will therefore have a lower ionization energy since it wants to lose that electron. (You can also think of the charges each of the atoms have: Na is +1 while Al is +1 or +3).