noun Physics, Chemistry.
THINK YOU’VE GOT A HANDLE ON THIS US STATE NICKNAME QUIZ?
Words nearby radioactivity
Example sentences from the Web for radioactivity
This would allow an estimate of the energy still left in the Martian core from a combination of its formation and radioactivity, a key element in understanding what geological activity might still be possible there.
“It is probably the purest environment in terms of radioactivity on Earth,” says Gioacchino Ranucci, a Borexino member.We still don’t really know what’s inside the sun—but that could change very soon|Charlie Wood|November 30, 2020|Popular Science
His calculations were in error, however — not because he was bad at math, but because he didn’t know about radioactivity.
Speculation: The scorch might have been made by radioactivity attendant upon the resurrection.
This new virus strain was accidentally produced in the course of some experiments with radioactivity.Operation R.S.V.P.|Henry Beam Piper
Twenty minutes after the irradiation period, the radioactivity of the calcium standards is measured by the same instrument.
Later on, radioactivity from silver (silver-110m) can be measured using a longer counting time.
Since the atomic wars, the increased radioactivity of the earth undoubtedly stimulates mitosis of the malignant cells.The Star Lord|Boyd Ellanby
Traces of natural radioactivity can be found, in fact, in all substances on earth.Atoms, Nature, and Man|Neal O. Hines
British Dictionary definitions for radioactivity
Medical definitions for radioactivity
Scientific definitions for radioactivity
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.
Cultural definitions for radioactivity
The emission of elementary particles by some atoms when their unstable nuclei disintegrate (see half-life). Materials composed of such atoms are radioactive. (See alpha radiation, beta radiation, and gamma radiation.)