noun Physics, Chemistry.
Origin of radioactivity
Examples from the Web for radioactivity
Contemporary Examples of radioactivity
Speculation: The scorch might have been made by radioactivity attendant upon the resurrection.10 Reasons the Resurrection Really Happened
April 10, 2009
Historical Examples of radioactivity
The place was still hot, but it was thermal heat, not radioactivity.The Measure of a Man
The amounts and kinds of radioactivity released to the environment.Atoms, Nature, and Man
Neal O. Hines
Remove them and measure the radioactivity produced from the sample.The Atomic Fingerprint
The owlies had learned what radioactivity meant, back when they fought the humans.Duel on Syrtis
Poul William Anderson
They were unable to venture into his old one because of the radioactivity and micro-organisms.Diplomatic Immunity
1899, from French radioactivité, coined 1898 by the Curies; see radioactive.
A Closer Look: In the nuclei of stable atoms, such as those of lead, the force binding the protons and neutrons to each other individually is great enough to hold together each nucleus as a whole. In other atoms, especially heavy ones such as those of uranium, this energy is insufficient, and the nuclei are unstable. An unstable nucleus spontaneously emits particles and energy in a process known as radioactive decay. The term radioactivity refers to the particles emitted. When enough particles and energy have been emitted to create a new, stable nucleus (often the nucleus of an entirely different element), radioactivity ceases. Uranium 238, a very unstable element, goes through 18 stages of decay before becoming a stable isotope of lead, lead 206. Some of the intermediate stages include the heavier elements thorium, radium, radon, and polonium. All known elements with atomic numbers greater than 83 (bismuth) are radioactive, and many isotopes of elements with lower atomic numbers are also radioactive. When the nuclei of isotopes that are not naturally radioactive are bombarded with high-energy particles, the result is artificial radioisotopes that decay in the same manner as natural isotopes. Each element remains radioactive for a characteristic length of time, ranging from mere microseconds to billions of years. An element's rate of decay is called its half-life. This refers to the average length of time it takes for half of its nuclei to decay.