alpha particle: A type of ionizing radiation, physically equivalent to the nucleus of a helium atom (because it consists of two protons and two neutrons). Alpha particles carry away some of the energy that had been in the nucleus from which it had been emitted. That energy will be deposited into any material with which it collides. If alpha particles collide with living tissue, they can be very biologically damaging. Alpha particles are released by some radioactive atoms, including plutonium, polonium, radium and uranium.
atom: (adj. atomic) The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.
atomic number: The number of protons in an atomic nucleus, which determines the type of atom and how it behaves.
decay: (for radioactive materials) The process whereby a radioactive isotope — which means a physically unstable form of some element — sheds energy and subatomic particles. In time, this shedding will transform the unstable element into a slightly different but stable element. For instance, uranium-238 (which is a radioactive, or unstable, isotope) decays to radium-222 (also a radioactive isotope), which decays to radon-222 (also radioactive), which decays to polonium-210 (also radioactive), which decays to lead-206 — which is stable. No further decay occurs. The rates of decay from one isotope to another can range from timeframes of less than a second to billions of years.
eject: To suddenly or forcefully push or jettison something from its position, container or housing.
equilibrium: A condition where things are in balance. It’s due to opposing forces equaling (or cancelling) each other out.
force: Some outside influence that can change the motion of a body, hold bodies close to one another, or produce motion or stress in a stationary body.
half-life: The time it takes for half of some quantity of a radioactive isotope to decay (transform) into a new isotope.
interim: An adjective describing some intermediate point in time or place.
isotopes: Different forms of an element that vary somewhat in mass (and potentially in lifetime). All have the same number of protons in their nucleus, but different numbers of neutrons.
lead: A toxic heavy metal (abbreviated as Pb) that in the body moves to where calcium wants to go (such as bones and teeth). The metal is particularly toxic to the brain. In a child’s developing brain, it can permanently impair IQ, even at relatively low levels.
morph: Short for metamorphose, it means to change or transform from one form to another (such as from a caterpillar to a butterfly) or from one shape to another. (in non-living systems) It refers to some thing, policy or activity that has undergone change, becoming something that looks or seems new and different.
neutrino: A subatomic particle with a mass close to zero. Neutrinos rarely react with normal matter. Three kinds of neutrinos are known.
neutron: A subatomic particle carrying no electric charge that is one of the basic pieces of matter. Neutrons belong to the family of particles known as hadrons.
nucleus: Plural is nuclei. (in biology) A dense structure present in many cells. Typically a single rounded structure encased within a membrane, the nucleus contains the genetic information. (in astronomy) The rocky body of a comet, sometimes carrying a jacket of ice or frozen gases. (in physics) The central core of an atom, containing most of its mass.
positron: A subatomic particle with the mass of an electron, but a positive electrical charge. It is the antimatter counterpart to the electron. So when electrons and positrons collide, they annihilate each other, releasing energy.
proton: A subatomic particle that is one of the basic building blocks of the atoms that make up matter. Protons belong to the family of particles known as hadrons.
radiation: (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.
radioactive: An adjective that describes unstable elements, such as certain forms (isotopes) of uranium and plutonium. Such elements are said to be unstable because their nucleus sheds energy that is carried away by photons and/or and often one or more subatomic particles. This emission of energy is by a process known as radioactive decay.
radioactive decay: A process by which an element is converted into a lighter element through the shedding of subatomic particles (and energy).
radon: A radioactive member of the noble gas family. It is naturally given off by some rocks in the soil. When it accumulates in homes or water supplies, it can pose a health hazard.
shell: (in physics) The orbital paths that electrons take around the nucleus of an atom.
subatomic: Anything smaller than an atom, which is the smallest bit of matter that has all the properties of whatever chemical element it is (like hydrogen, iron or calcium).
thorium: A naturally radioactive element which appears as a silvery metal when it is pure. It reacts chemically with air, turning black on its surface. It is found in some minerals, and can be used to trace the source of some mineral grains that are carried long distances by water or wind. Its scientific symbol is Th.
trillion: A number representing a million million — or 1,000,000,000,000 — of something.
universe: The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).
