Some of these particles are known as ionizing particles. These are particles with enough energy to knock electrons off atoms or molecules. The degree of radioactivity depends on the fraction of unstable nuclei and how frequently those nuclei decay. The effect of radioactivity also depends on the type and energy of the particles produced during nuclear decay.
For example, neutrinos pass constantly through the Earth, while alpha particles are blocked by a sheet of paper. Radioactivity can cause damage in materials and in plant, animal, and human tissue. Scientists and engineers use radioactivity as a source of heat for satellites, for medical imaging, for targeted cancer treatments, for radiometric dating, and for research into the laws of nature and the origin of matter.
It is impossible to predict when an individual radioactive atom will decay. The half-life of a certain type of atom does not describe the exact amount of time that every single atom experiences before decaying. Rather, the half-life describes the average amount of time it takes for a large group of amounts to reach the point where half of the atoms have decayed. The half-life of a radioactive material can be changed using time dilation effects.
According to relativity, time itself can be slowed down. Everything that experiences time can therefore be given a longer effective lifetime if time is dilated.
This can be done in two ways. Traveling at a speed close to the speed of light causes time to slow down significantly, relative to the stationary observer. For instance, a number of radioactive atoms shot through a tube at high speed in the lab will have their half-life lengthened relative to the lab because of time dilation. This effect has been verified many times using particle accelerators.
Time can also be dilated by applying a very strong gravitational field. For instance, placing a bunch of radioactive atoms near a black hole will also extend their half-life relative to the distant observer because of time dilation.
The half-life of radioactive decay can also be altered by changing the state of the electrons surrounding the nucleus. In a type of radioactive decay called "electron capture", the nucleus absorbs one of the atom's electrons and combines it with a proton to make a neutron and a neutrino.
The more the wavefunctions of the atom's electrons overlap with the nucleus, the more able the nucleus is to capture an electron. Typically, the most stable form of an element is the most common in nature. However, all elements have an unstable form. Unstable forms emit ionizing radiation and are radioactive. There are some elements with no stable form that are always radioactive, such as uranium. Elements that emit ionizing radiation are called radionuclides.
When it decays, a radionuclide transforms into a different atom - a decay product. The atoms keep transforming to new decay products until they reach a stable state and are no longer radioactive. The majority of radionuclides only decay once before becoming stable. Those that decay in more than one step are called series radionuclides. The series of decay products created to reach this balance is called the decay chain decay chain The series of decays or transformations that radionuclides go through before reaching a stable form.
For example, the decay chain that begins with Uranium culminates in Lead, after forming intermediates such as Uranium, Thorium, Radium, and Radon Also called the "decay series. Each series has its own unique decay chain.
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