I notice that online definitions of this experimental law always say, molecules or atoms.
From the Wikipedia article on Avogadro's Law:
$${\frac {V_{1}}{n_{1}}}={\frac {V_{2}}{n_{2}}}$$ The equation shows that, as the number of moles of gas increases, the volume of the gas also increases in proportion. Similarly, if the number of moles of gas is decreased, then the volume also decreases. Thus, the number of molecules or atoms in a specific volume of ideal gas is independent of their size or the molar mass of the gas.
In lumenlearning:
Key Points
- The number of molecules or atoms in a specific volume of ideal gas is independent of size or the gas’ molar mass.
This made me wonder if $n$ in the $PV = nRT$ can also be the number of atoms in that volume of gas. Taking a practical example, what is the answer to the following question?
Statement (I):
Atoms can neither be created nor destroyed.Statement (II):
Under similar conditions of temperature and pressure, equal volumes of gases do not contain an equal number of atoms.
My question is, if $P$, $V$ and $T$ are equal, can we say $n$ (number of atoms) are equal?
The answer given is that, no they need not be equal since only number of molecules will be equal. The gas can consist of a mixture of diatomic and triatomic molecules, we can have the same number of molecules but different number of atoms.
From what I read on Kinetic Molecular Theory, the volume occupied by the molecules of the gas is negligible compared to the volume of the gas itself. This is the central assumption. So I guess the law applied only to molecules and not atoms or the generic "particles" as how some sites define it.