We know the alpha particle is the nucleus of helium. It contains four subatomic particles - two protons and two neutrons. The protons and neutrons are further made of particles called up and down quarks. So why call an alpha particle a particle. And similarly, why do we say electrons, protons, neutrons etc. are particles, even though, they are made of particles?
I can understand the case of electrons, protons, and neutrons as when they were discovered and named, quarks were not discovered. But the helium nucleus is a different case.
I reckon talking about an English word's meaning changes in the frame of reference. We do not call a quark an object, although, an object could be any real or virtual thing. So in chemistry, I don't think calling an alpha particle a particle is a good practice. I do understand there are dust particles and all but we mention them only while talking about the macroscopic world. Not so in the case of chemistry. I hope you get my point.