An alpha particle has two protons and two neutrons, so it has a positive charge.
(Since it has two protons it is a helium nucleus.) It is produced from large
an alpha particle, the atom'smass
numberdecreases by four due to the
loss of the fournucleonsin
the alpha particle. Theatomic numberof
the atom goes down by exactly two, as a result of the loss of two protons – the
atom becomes a new element. Examples of this are when uraniumbecomesthorium,
due toalpha decay.
Alpha particles are commonly emitted by all of the largerradioactivenuclei
andradium, as well as thetransuranic
elements. Unlike other types of decay, alpha decay as a process must have a
minimum-size atomic nucleus which can support it. The smallest nuclei which have
to date been found to be capable of alpha emission are the lightest nuclides oftellurium(element
52), with mass numbers between 106 and 110. The process of emitting an alpha
sometimes leaves the nucleus in an excited state, with the emission of agamma
rayremoving the excessenergy.
Beta emission is when a high speed electron (negative charge) leaves the
nucleus. Beta emission occurs in elements with more neutrons than protons, so a
neutron splits into a proton and an electron. The proton stays in the nucleus
and the electron is emitted.
A nucleus which is in an excited state may emit one or more photons (packets of
electromagnetic radiation) of discrete energies. The emission of gamma rays does
not alter the number of protons or neutrons in the nucleus but instead has the
effect of moving the nucleus from a higher to a lower energy state (unstable to
stable). Gamma ray emission frequently follows beta decay, alpha decay, and
other nuclear decay processes.
Positron emission involves a particle that has the same mass as an electron but
a positive charge. The particle is released from the nucleus when a proton
splits into a neutron and positive electron.
Separation of some radioactive
Note the path of the beta particle is curved more
than the alpha. This is due to the mass.
A wiffle ball can curve more than a more massive