Real gases are those that:

A. only behave ideally at high pressures or low temperatures

B. have an even number of protons

C. are only available naturally in the earth's atmosphere

D. deviate from ideal behavior

E. are called real gases because their behavior can easily be modeled

Real gases are those, which deviate from ideal behavior.

Answer: Option D

Explanation:

Very tiny particles are present in real gases and occupying finite space by exerting some specific interactions between them. It takes as the reason for why it deviates from its behaviour. There is a lot of difference between a real gas and ideal gas. Ideal gas is the one that which is imaginary, and does not exist. Its characteristics are ideal, and all other real gases, try to follow them.

Real gases, are available in the atmosphere, but need not be naturally available. There is no relation between number of protons and nature. And, they won't behave ideally, at any conditions. We calculate the characteristics of a real gas using ideal gas equation, only because it is very difficult to determine their behaviour.