Unit 1 - Radioactive decay Flashcards
(8 cards)
What are the different types of radioactive decay?
Alpha decay–heavy isotopes: He2+ or α
Beta decay–neutron rich isotopes: e- or b-
Positron emission–proton rich isotopes: b+
Electron capture–proton rich isotopes: X-rays
Gamma-ray emission(g ): Decay of nuclear excited states
Spontaneous fission: very heavy isotopes
Alpha decay
The product nucleus has an atomic number that is two less, and a mass number that is four less than the original nucleus.
E.g americium-241 decay producing Neptunium:
Am (atomic: 95, mass: 241) -> Np (atomic: 93, mass: 237) + He (atomic: 2, mass: 4)
(half life, t1/2 = 432 years)
Beta decay
Neutron converted to a proton and an electron ejected
n -> p + e-
The product nucleus has an atomic number that is one more than the original nucleus. mass number remains the same.
E.g. carbon-14 decay
C (atomic: 6, mass: 14) -> N (atomic: 7, mass: 14) + e (atomic: -1, mass: 0)
Positron emission
Conversion of a proton to a neutron and a positron (positive electron).
Product nucleus has an atomic number that is one less than the original nucleus. the mass number remains the same.
E.g. copper-64 decay:
Cu (atomic: 29, mass:64) -> Ni (atomic: 28, mass: 64) + e (atomic: 1, mass: 0)
Electron capture
Conversion of a proton to a neutron (nucleus captures electron from inner orbital)
p + e -> n
Product nucleus has an atomic number that is one less than the original nucleus. the mass number remains the same. E.g. potassium-40 decay
K (atomic: 19, mass: 40) + e (atomic: -1, mass: 0) -> Ar (atomic: 18, mass: 40)
Further information on Electron capture
When another orbital electron fills the vacancy in the inner-shell an X-ray photon is emitted.
Gamma emission
Some cases of radioactive decay result in a product nucleus in an excited state which goes to a lower state with emission of electromagnetic radiation.
Spontaneous fission
A heavy nucleus splits into lighter nuclei with the release of energy.
