My textbook, Atkins' Physical Chemistry, 11th edition, by Atkins, de Paula, and Keeler, says the following:
The resulting expression
$$pV = nRT \tag{1A.4}$$
is the perfect gas law (or perfect gas equation of state). It is the approximate equation of state of any gas, and becomes increasingly exact as the pressure of the gas approaches zero. A gas that obeys eqn 1A.4 exactly under all conditions is called a perfect gas (or ideal gas). A real gas, an actual gas, behaves more like a perfect gas the lower the pressure, and is described exactly by eqn 1A.4 in the limit of $p \to 0$. The gas constant $R$ can be determined by evaluating $R = pV/nT$ for a gas in the limit of zero pressure (to guarantee that it is behaving perfectly).
A note on good practice Despite 'ideal gas' being the more common term, 'perfect gas' is preferable. As explained in Topic 5B, in an 'ideal mixture' of A and B, the AA, BB, and AB interactions are all the same but not necessarily zero. In a perfect gas, not only are the interactions all the same, they are also zero.
My questions here relate to this part:
A note on good practice Despite 'ideal gas' being the more common term, 'perfect gas' is preferable. As explained in Topic 5B, in an 'ideal mixture' of A and B, the AA, BB, and AB interactions are all the same but not necessarily zero. In a perfect gas, not only are the interactions all the same, they are also zero.
It seems that the authors here are implying that a "perfect gas" and an "ideal gas" are synonymous, but my research indicates that they are actually different concepts. Are these two concepts the same, or are they different? How should one think about (distinguish) these two concepts?
What do the authors mean when they say that "in an 'ideal mixture' of A and B, the AA, BB, and AB interactions are all the same but not necessarily zero"? And what is meant by the interactions being "zero" here?
What do the authors mean when they say that "in a perfect gas, not only are the interactions all the same, they are also zero"? And what is meant by the interactions being "zero" here?
I would greatly appreciate it if people would please take the time to clarify these points.