An Introduction to Ionization Energies:

Ionization Energy

Students

Notice the chlorine atom went from having no charge to having a -1 charge.

In other instances an atom will lose an electron as is seen below with a Sodium atom. In this case, when the sodium atom loses the electron it gains a +1 charge.

Once an atom has completed an electron transfer, it is no longer considered an atom. Instead, we now refer to it as an "Ion" of that element. Atoms can only be neutral. Ions can only be charged. Compounds that are made up of ions are called "ionic compounds."

The size of the ion is different from the size of the atom. As you add electrons, the ion gets larger and as you subtract electrons, the ion gets smaller. This can easily be explained if you think about the repulsion forces you create each time you add an electron to an atom. With each new electron, the repulsion forces increase. Thus, the electrons around the ion are occupying a larger volume. However, when you remove electrons, the inner shells of electrons become the valence shell and thus your ion is smaller.

Now that you understand what an ion is, you will understand what the ionization energy is. The ionization energy is the amount of energy required to remove one electron from an atom. Thus, it measures how strong the outermost electron is attached to the atom. Some atoms have more than one ionization energy. We will talk more about this in the background reading section.

This lab is designed to help you explore the concept of ionization energies.