Explain the difference in ionization energies of alkali and alkaline earth metals?

Ionization energy increases as you move from the bottom left of to the top right.

Ionization energy is the energy to remove an electron. It's easier to remove one electron from an alkali metal than an alkaline earth metal because the element will then obtain noble gas configuration (filled 8 electrons in the valence shell).

There are multiple ionization energies. So what I described above is for the first ionization energy (remove one electron). The second ionization energy would be the energy to remove a second electron. The second ionization energy would be massively higher for an alkaline earth metal because it would obtain noble gas configuration, whereas the alkali metal would be pulling an electron off a filled valence shell (very difficult)