How do you expect the size of the atoms to change as you go from neon to argon to krypton

The number of energy levels will increase.

Explanation:

As they are all Noble Gases, they are all in the same family. However, as you go further down the list of Noble Gases, the period number increases. The period number shows the number of energy levels. Hence, an increase in energy levels.

plasma is the state of matter where the substance is ionized and has no definite shape or volume. the fact of being ionized makes the substance a good electrical conductor.