Welcome to Deep Dive. Here we pick 1 question or concept (and it may be a small one like here), and without distraction go deep down into the heart of that concept.

There will be no pictures for distraction and decoration.

You will not learn everything about Periodic Trends or even Ionization Energy trends today.

But what you learn, you will learn well!

Long ago, in the spring of 2010, there was a question about electronic configuration and ionization energy in the AP Chemistry final. Today we are going to use the second part of the problem as a base to do a deep dive!

The reaction given was:

2 Al(s) + 3 Zn2+(aq) → 2 Al3+(aq) + 3 Zn(s)

Q2 was: “Which species, Zn or Zn2+, has the greater ionization energy? Justify your answer.”

Now the equation given above has nothing to do with this reaction!

Let’s answer this question with a series of other questions:

1. What is ionization energy? Well, it is the energy needed to ionize something

a. What is ionize? To make into an ion! Memorize is to make into a memory, randomize is to make random… you get the gist.

b. So it is the energy needed to make something into an ion! Specifically into a cation (+)

2. Why do you need energy for that? Because electrons are attracted to the nucleus. Pulling one out is a bit like pulling teeth that are attracted to your gums! (Terrible analogy alert)

3. Does it follow that adding electrons (electron affinity) would then not require but release energy? YES!

4. OK, how do you determine if IE (ionization energy is now our friend and deserves an abbreviation) is higher or lower?

Does pulling that electron out make the atom an octet?
low IE
NO–high IE
Actually it takes it away from an octet –SUPER HIGH IE!!

In fact, every extra electron that you pull is going to make the IE higher and higher UNLESS….

Yes, you got it! Unless you are going to an octet.

Analogy time… Every extra tooth I pull from you is going to hurt more and more until you have no more teeth left.

See that analogy didn’t work.

Let’s try this. Every dollar you steal from a very poor person is going to make him angrier and angrier until he has lost enough and now becomes eligible for … say… state support! Then you hit a low point, and you continue to make him angrier as you steal more. Makes sense?

So here neither Zn nor Zn2+ have an octet, so who’s going to be angrier when we pull an electron away from them? Zn2+ is right, because it has already lost two electrons. Therefore Zn2+ has the higher ionization energy.

Let’s generalize:

Every cation will have a higher IE than the atom, unless you are leading that cation to an octet by pulling an electron.

Every anion will have a lower IE than the atom, unless the anion already has an octet!

Please comment on the deep dive: Deep enough? Too deep? Need to know more?