What image can you draw to represent ionization energy?
You could draw it using Lewis structures, where valence
electrons are represented by dots. You can also express it in
equation form. The first ionization of calcium, for instance, could
be expressed as: Ca --> Ca+ + e-
As you can see, neutral calcium loses an electron to form the
calcium +1 cation. Of course, we know that calcium will lose
another electron as well, which can be expressed in the equation
for the second ionization of calcium: Ca+ --> Ca++ + e-
Normally, calcium will not experience a third ionization,
because with two valence electrons, it has now achieved a full
octet and is isoelectronic with argon.