Radioactive Decay

Radioactivity is the spontaneous emission of radiation from an unstable nuclei, usually an isotope. Isotopes (atoms with more neutrons than protons) tend to be unstable and will emit radioactivity order to reach greater stablity.

Atomic number is the number of protons. The number of protons determines the type of atom. For example, all carbon atoms have 6 protons, all nitrogen atoms have 7 protons. If the number of protons changes, the element changes. Mass number is the total mass of the atom (the number of protons and the number of neutrons added together). If the number of neutrons does not exactly equal the number of protons, then the atom is an isotope of that element. For example, carbon (¹²C) has 6 protons and 6 neutrons. Carbon-14 (¹⁴C) has 6 protons and 8 neutrons, carbon-13 (¹³C) has 6 protons and 7 neutrons. ¹⁴C and ¹³C are isotopes of ¹²C.

• Law of radioactive decay
• Fundamentals of Radiation
• Radioactivity
• Radiation Fundamentals
• Artificial Radiation Sources
• Radioactivity and the Nuclear Structure
• Absorption and Emission of Radiation by an Atom
• Radiation
• Radiation Information Network
• What you need to know about radiation
• Centenial of the discovery of radioactivity
• Nature of Radiation
• Radiation Related Frequently Asked Questions

There are three types of radioactive decay processes, which are listed below.

Alpha Radiation

The emission of alpha particles ( a ), or alpha radiation ,is one of the common pathways by which a radioactive isotope can decay to a stable isotope. An alpha particle is essentially a helium nucleus, with 2 protons and 2 neutrons and a 2⁺ charge. The emission of alpha radiation causes the atomic number of the nucleus to decrease by two and the atomic mass to decrease by four.

Beta Radiation

The emission of a beta particle ( b ), or beta radiation , is the emission of a high speed electron from an unstable nucleus. Beta particles have the same mass and charge (-1) as electrons. The electron is formed on the spot within the nucleus by the breakdown of a neutron into a proton and electron. The electron is released from the system. The proton that was formed remains behind in the nucleus.

The emission of a beta particle has the effect of leaving the nuclear mass unchanged but increasing the nuclear charge by one, and so the element produced by beta decay is one column to the right in the periodic chart from the original element. Carbon-14 is one radioactive isotope which undergoes beta decay. Its decay reaction is:

Gamma Radiation

Gamma radiation ( g ) is the emission of very high-energy photons, not the emission of particles. Many alpha and beta emissions are accompanied by gamma emissions because the nucleus loses excess energy through gamma radiation. Emission of gamma rays does not change the element, or isotopes, as gamma rays do not have mass or charge.

• Gamma Radiation - including a diagram.
• Medicine Wordlwide - Beta Decay.
• The Particle Adventure Home Page - Scroll down and click on "particle decay." Have fun!
• Electormagnetic Interaction: Gamma incident