Can you explain how to determine which of a number of elements with their respective different orbitals would have the highest first ionization energy and how to find this. Eg. Comparing Li, Ca, N and F

Yes, the main difference lies in the size of the atom of the element.

This includes the number of shells and the force of electrostatic attraction.

Going down a group, you have an additional shell, hence the distance from the nucleus to the outermost electron (the electron to be removed for ionisation) is large, and the larger the easier to remove it. Hence a 'small' IE (ionisation energy) is required.

Going across a period, you have the same number of shells, but there are more protons and electrons. Hence, the ionisation energy increases, because the electrostatic force is greater across the group.

From that, you should be able to answer your question.

There are more details I might add. Ask away if you need any more.