Explain why the ionization energy of aluminum is less than that of nitrogen?

Question

Based on the actual configurations of the elements, explain why the ionization energy of aluminum is less than that of nitrogen

Answer 1

There are a number of reasons for this.

The first is shielding. It is the protons that attract the electrons, of course. But inner groups of electrons force the outer groups of electrons further and further away from the protons, where there is less attraction because of the distance. This is why every element has a lower ionization energy than the element directly above it in the periodic table. Aluminum is one row down from nitrogen, so it will have more shielding and it will be easier to steal those outer electrons.

The second reason is electron shell configuration. Not only are inner electrons repelling outer electrons, the outer electrons are repelling each other. They want to be in a stable configuration themselves... the most stable sets involve all of each type of orbital either filled or half-filled. So let's look at what we have:

Aluminum has 2 3s electrons and 1 3p electron by default. If it just lost that 3p, it would be pretty stable with a full 3s set and nothing in the p's. Nitrogen, on the other hand, has 2 2s and 3 2p electrons. Losing one of the p's isn't going to help much at all... it will still have 2 rattling around. On the other hand, if it GAINED another p, it would have all the p orbitals half-filled, which is a good state to be in. Yet another reason why nitrogen holds onto electrons way better than aluminum.

Hope that helps!

Answer 2

Ionization energy is the energy required to remove a single outer electron from an atom. So, a couple of different factors contribute to the difference between aluminum and nitrogen. Mainly, the outer electrons in aluminum are in the 3rd shell while nitrogen's outer electrons are in the 2nd shell. Since the electron in Al is in a different energy shell, is it farther away on average from the nucleus and so is "held on to" less tightly. Consequently, it will be easier to remove.

Answer 3

Aluminum (Al) has an atomic number of 13, it's electron configuration is 1s2 2s2 2p6 2s2 2p1 and belongs to the 3 period, IIIA group of the P.T.

Nitrogen (N) has an atomic number of 7, it's electron configuration is 1s2 2s2 2p3, so it belongs to the 2 period and the VA group of the P.T.

Now, the ionization energy decreases to the left and down of the P.T. Aluminum locates left (IIIA versus VA) and down (3 period versus 2 period) to nitrogen so it's ionization energy is less than that of nitrogen.