Radioactivity

An unstable nucleus spontaneously decays into a more stable nucleus.

The new nucleus has less mass per nucleon than the unstable one

Isotope

Has more neutrons

The missing mass is released as energy

E=mc²

C=(3×10^8)

MeV

Megaelectronvolts

Three types of decay:

Alpha, beta, gamma

Alpha decay

A nucleus splits into an alpha particle and a new nucleus

Beta decay

A neutron decays into a proton and an electron.

Gamma decay

Does not change the number of protons and neutrons in the nucleus

Beta decay is evidence for the presence of a fourth force of nature

The half-life of an isotope is the time it takes for half of the starting amount to decay.

Different isotopes have different half-lives.

When isotopes besides carbon are used, it is generally called radiometic dating.

Radioactive materials produce high-energy particles when they decay