Question: how is an alpha particle different to a helium nucleus?
Answer: atom is a nucleus + electrons, a helium atom is thus its nucleus (2 protons, 2 neutrons) and its 2 electrons. An alpha particle is just the nucleus. Alpha "rays" are actually high speed particles. ... Helium atoms are composed of a nucleus with 2 protons, 2 neutrons, as well as an electron shell with 2 electrons.