Is an alpha particle a helium nucleus?
I suspect what your teacher really meant to say was that, while the particle is identical to a helium nucleus, it never came from an actual helium atom. But I see two problems with this: -It almost certainly will form the nucleus of a helium atom in the future, when it eventually hits something and picks up a couple of electrons -It’s kind of a meaningless semantic distinction I think most scientists would be comfortable with the statement that an alpha particle is basically a helium nucleus that got shot out of a larger nucleus, and wouldn’t worry about the question of whether it’s “really” a helium nucleus or not.
