In the periodic systems of elements the ordinal number sorts elements by their nuclear charge (their protons).

See also Nucleus, Proton and Mass Number.

The alpha decay is a corpuscular radiation. Two protons and two neutrons (a helium core) are emitted from the atomic nucleus. Because of the high biological effectiveness, the use of alpha particle radiation is not allowed in diagnostic nuclear medicine.

An anion is a negative charged ion; the atom has more electrons than protons. Anions are attracted from the positively charged anode. This is a basic part for producing radiation in the x-ray tube.

(AMU) is equal to the mass of one-twelfth of a carbon-12 atom (6 protons + 6 neutrons (+ 6 electrons)), a 'very' little less than 1.66 x 10^-24 gram.

See also Mass Number and Atomic Mass.

The atomic number of a nucleus is the number of protons contained in the nucleus.