alpha decay - Alphastrahlung
When an isotope that is unstable decays by emitting an alpha particle it releases a helium atom. This results in new element with an atomic mass (mass of protons and neutrons) reduced by 4. The atomic number (number of protons) reduced by 2.
The equation in general form is as follows.
$${ ^{M}_{Z} X \rightarrow ^{M-4}_{Z-2} Y + ^{4}_{2} He }$$
example $${ ^{222}_{88} Ra \rightarrow ^{218}_{86} Rn + ^{4}_{2} He }$$
beta decay - Betastrahlung
Another type of decay is the release of a beta particle, a fast electron released from the nucleus. In the atom nucleus, one neutron turns into a proton and a fast electron, called a beta particle. The resulting element now has one proton more but still the same mass. So, the atomic number has increased by one and the mass number stays the same.
$${ ^{M}_{Z} X \rightarrow ^{M}_{Z+1} Y + ^{0}_{-1} e }$$
example - the decay of carbon-14 (C-12 and C-13 are not radioactive) $${ ^{14}_{6} C \rightarrow ^{14}_{7} N + ^{0}_{-1} e }$$
gamma decay - Gammastrahlung
After an alpha or beta decay the nuclei may also stabilise by emmiting energy in form of radiation. This radiation is known as gamma decay.
summary of properties - Übersicht der Eigenschaften
| type of decay | particle emmited | speed | penetration |
|---|---|---|---|
| $${ \alpha }$$ | nucleus of helium $${ ^{4}_{2} He }$$ | about 5% the speed of light | stopped by paper |
| $${ \beta }$$ | an electron $${ ^{0}_{-1} e }$$ | can vary but up to 99% of the speed of light | stopped by aluminium (greater than ~3 mm) |
| $${ \gamma }$$ | radiation | speed of light | lead reduces the radiation |