Nuclei with odd number of protons and odd number of neutrons can break apart {radioactivity}|. Nuclei with even numbers of both protons and neutrons are stable, because orbits are full. Bigger nuclei are less stable, because neutron number is more than proton number. Radioactive decay happens randomly. Temperature, pressure, and other substances do not affect it. However, it can increase above 10^6 K.
Radioactive material takes time {half-life, radioactivity}| to become half as radioactive. Half-life can be several hours to billions of years. Short-half-life isotopes emit high-velocity alpha particles. Long-half-life atoms emit low-velocity alpha particles.
Radioactive nuclei can lose clusters {alpha particle, radiation} with two protons and two neutrons. Paper can stop alpha particles.
Radioactive nuclei can lose electron {beta particle}|. Neutron to proton and electron conversion makes beta particles. Aluminum foil can stop beta particles.
Radioactive nuclei can lose high-energy radiation {gamma particle}|. Five meters of concrete can stop gamma particles.
Devices {Geiger counter} can measure inert-gas ionization in 2000-V potential. Ionization causes current cascade. Current is proportional to ionization.
Devices {proportional counter} can measure gas ionization in 1000-V potential. Current is sensitive to voltage change.
Devices {scintillation counter} can measure sodium-iodide, anthracene, or naphthalene fluorescence. Photomultiplier detects visible light.
Radioactivity detection can use tiny bubbles in saturated fluid {bubble chamber}.
Radioactivity detection can use condensation trails in saturated vapor {cloud chamber}.
Radioactivity detection can combine bubble and spark chamber {streamer chamber}.
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Date Modified: 2022.0225