Isotopes of Hydrogen

- Isotopes = atoms with differing numbers of neutrons

- Mass number = the combined number of protons and neutrons
- - Isotopes of an element behave differently
- - Some isotopes are radioactive and decay until they become non-radioactive stable isotopes
- - Emit high-energy radiation

- Half-life = the amount of time it takes for one-half of the atoms to give off radiation and decay
- - Different radioscopes have different half-lives
- - Ranging from fractions of a second to billions of years
- - Uranium-235: Used in commercial nuclear power and Has a half-life of 700 million years

- Atoms may also gain or lose electrons to become ions, electrically charged atoms