Society Members full access to the journal is a member benefit. SVS Member login. Atomic Structure Nucleus Contains Protons And Neutrons Matter Science Relative Atomic Mass Protons The electron mass symbol. . Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle helium nucleus and thereby transforms or decays into a different atomic nucleus with a mass number that is reduced by four and an atomic number that is reduced by two. With our money back guarantee our customers have the right to request and get a refund at any stage of their order in case something goes wrong. Likewise the conservation of the total kinetic energy is expressed by. Average Atomic Mass and definition of atomic mass unit. While atomic mass is an absolute mass relative isotopic mass is a dimensionless number with no units. There is a slight difference since the relative atomic mass has no units. ...