from The Century Dictionary and Cyclopedia
- n. A radioactive element; an elementary chemical substance which undergoes spontaneous disintegration, with or without the emission of Becquerel rays, and which is either produced from or itself produces an element which is the source of such a radiation.
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Next, this unstable atom, this new radio-element which we have called "radio-phosphorus" decomposes exponentially with a half-life of three minutes.
At its center was a tiny capsule of synthetic radio-element, surrounded by the converting screens that shifted its radiation far down the spectrum.
Next, this unstable atom, this new radio-element which we have called decomposes exponentially with a half-life of three minutes.
The time necessary for the disappearance of half the atoms, called the half-life, is a fundamental characteristic of each radio-element; according to the substance the value of the half-life varies between a fraction of a second and millions of years.