1. Radioactivity
Radioactive decay

2. What is Radioactivity
The isotopes of many atoms are unstable (have extra energy). These are called radioisotopes.
Radioisotopes emit this extra energy (radiation), to become more stable, by splitting up.
When a radioisotope splits up new atoms with different atomic and mass numbers are formed.
Radioisotopes that emit radiation are radioactive. The emission process is called radioactivity.
Radioactivity is a totally random (spontaneous) process. It cannot be predicted.

3. Losing the Energy Losing the Energy
A radioisotope can lose energy by emitting three different types of radiation:
1. Alpha radiation (often called alpha particles).
2. Beta radiation (often called beta particles).
3. Gamma radiation (often called gamma rays).

4. Alpha Radiation Alpha particles are:
1. Made up of two protons and two neutrons (the same as the nucleus of a Helium atom).
2. Have a mass number of 4 and an atomic number of 2.
3. Are positively charged.

5. The picture below shows an Americium atom (mass number 241) emitting energy in the form of an alpha particle to form an atom of Neptunium (mass number 237).
241Am Np He

6. Alpha Decay Write the alpha decay of thorium -230
23090Th 42He Ra
Write the alpha decay of Radium – 226
22688Ra 42He Rn

7. Beta Radiation Beta particles (given the symbol b ) are:
1. Electrons that are emitted from the nucleus of a radioisotope.
2. Have almost no mass (the same as an electron).
3. Are negatively charged.

8. Beta Decay
During Beta Decay, one neutron is split into one positive proton and one negative electron.

9. Beta Decay Write the equation for the beta decay of Magnesium -27
2712Mg 0-1e Al
Write the equation for the beta decay of Sulfur – 35
3516S 0-1e Cl

10. Gamma Radiation Gamma radiation :
1. Is high-energy (short wavelength / high frequency) electromagnetic radiation.
2. Has no mass.
3. Has no charge.

11. Practice Problems
Write a balanced nuclear equation for the radioactive decay of iron-60 to cobalt-60, and determine the type of decay.
Write a balanced equation for the nuclear reaction in which uranium-234 decays to form thorium-230, and determine the type of decay.

12. Answers
6026Fe Co e
23492U Th He