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Secondly, he found the charge-to-mass ratio of alpha particles to be half that of the hydrogen ion. Rutherford proposed three explanations: 1) an alpha particle is a hydrogen molecule (H 2) with a charge of 1 e; 2) an alpha particle is an atom of helium with a charge of 2 e; 3) an alpha particle is half a helium atom with a charge of 1 e.
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or "decays" into a different atomic nucleus, with a mass number that is reduced by four and an atomic number that is reduced by two.
m = mass of the alpha particle = 6.64 × 10 −27 kg; k = Coulomb constant = 8.987 × 10 9 N·m 2 /C 2; When the alpha particle passes close to the nucleus barely missing it, such that the impact parameter b is equal to the radius of a gold nucleus (7 × 10 −15 m), the estimated deflection angle θ will be 2.56 radians (147°).
The alpha particle is an especially strongly bound nucleus, helping it win the competition more often. [57]: 872 However some nuclei break up or fission into larger particles and artificial nuclei decay with the emission of single protons, double protons, and other combinations. [55] Beta decay transforms a neutron into proton or vice versa.
210 Po is an alpha emitter that has a half-life of 138.376 days; [1] it decays directly to stable 206 Pb. The majority of the time, 210 Po decays by emission of an alpha particle only, not by emission of an alpha particle and a gamma ray; about one in 100,000 decays results in the emission of a gamma ray. [10]
The X++ particle was later determined to have mass 4 and to be just a low-energy alpha particle. [8]: 25 Nevertheless, Rutherford had conjectured the existence of the deuteron, a +1 charge particle of mass 2, and the neutron, a neutral particle of mass 1. [32]: 396 The former is the nucleus of deuterium, discovered in 1931 by Harold Urey. [34]
The following are among the principal radioactive materials known to emit alpha particles. 209 Bi , 211 Bi , 212 Bi , 213 Bi 210 Po , 211 Po , 212 Po , 214 Po , 215 Po , 216 Po , 218 Po
It undergoes alpha decay to 224 Ra. Occasionally it decays by the unusual route of cluster decay, emitting a nucleus of 20 O and producing stable 208 Pb. It is a daughter isotope of 232 U in the thorium decay series. 228 Th has an atomic weight of 228.0287411 grams/mole. Together with its decay product 224 Ra it is used for alpha particle ...