In alpha decay, an energetic helium ion (alpha particle) is ejected, leaving a daughter nucleus of atomic number two less than the parent and of atomic mass number four less than the parent.An example is the decay (symbolized by an arrow) of the abundant isotope of uranium, In beta-minus decay, an energetic negative electron is emitted, producing a daughter nucleus of one higher atomic number and the same mass number.In 1934 it was discovered that radioactivity could be induced in ordinary matter by artificial transmutation.
A third type of radiation, gamma radiation, usually accompanies alpha or beta decay.
Gamma rays are photons (photon) and are without rest mass or charge.
The process continues until a stable nuclide has been formed.
The emissions of the most common forms of spontaneous radioactive decay are the alpha (alpha particle) (α) particle, the beta (beta particle) (β) particle, the gamma (gamma ray) (γ) ray, and the neutrino.
Half-lives range from more than 1,000,000,000 years for some nuclei to less than 10 second (see below Rates of radioactive transitions (radioactivity)).
The product of a radioactive decay process—called the daughter of the parent isotope—may itself be unstable, in which case it, too, will decay.Gamma rays are electromagnetic radiations such as radio waves, light, and X-rays.Beta radioactivity also produces the neutrino and antineutrino, particles that have no charge and very little mass, symbolized by ν and ν, respectively.Neutrons and protons are, of course, the basic building blocks of complex nuclei, having approximately unit mass on the atomic scale and having zero charge or unit positive charge, respectively. It is rapidly captured by nuclei in matter; otherwise, in free space it will undergo beta-minus decay to a proton, an electron, and an antineutrino with a half-life of 12.8 minutes.The proton is the nucleus of ordinary hydrogen and is stable.(Alternatively to gamma emission, an excited nucleus may transform to a lower energy state by ejecting an electron from the cloud surrounding the nucleus.