Alpha Particles
Alpha particles consist of two protons and two neutrons. They have a total energy of approximately 5MeV.
A nucleus that emits an alpha particle loses 2 from its atomic number and 4 from its mass number. It becomes an isotope of the element two places down in the periodic table.
Alpha particles can be written as He2+ or 42He2+ because they are identical to a helium nucleus. They have have low penetration, they can be stopped by a piece of paper, and are a highly ionizing form of particle radiation.
Alpha particles are emitted by radioactive nuclei such as uranium, thorium, actinium, or radium in a process known as alpha decay.
Some of the products of alpha decay can be in the form of gases and these represent serious health hazards