Final answer:
Alpha particles are emitted from the nuclei of heavy radioactive elements, such as uranium-238, and are composed of 2 protons and 2 neutrons, with a 2+ charge.
Step-by-step explanation:
The type of radiation that is emitted from the nucleus of heavy radioactive elements is typically an alpha particle, which is a helium nucleus consisting of 2 protons and 2 neutrons. An example of an alpha emitter is uranium-238 which decays into thorium-234 by emitting an alpha particle. This process can be represented as ^{238}_{92}U → ^{234}_{90}Th + ^{4}_{2}He. Alpha particles have a 2+ charge and are significant in terms of changing both the atomic number and the mass number of the original element, decreasing the atomic number by two and the mass number by four.