Radioactivity is the spontaneous emission of particles or energy from unstable atomic nuclei to become more stable. It was discovered in 1896 by Henri Becquerel when studying uranium salts that emitted rays and could burn skin. Later, Marie and Pierre Curie isolated the radioactive elements radium and polonium, and defined their property of half-life. There are three main types of radioactive emissions - alpha, beta, and gamma rays - which were categorized by their ability to ionize atoms as either ionizing or non-ionizing radiation.

1. Radioactivity

2. Radioactivity
• Unstable nucleus spontaneously emits small
particles and/or energy in order to attain a more
stable nuclear state.

3. 1895 – Wilhelm Roentgen
• Nobel Prize in physics in
1901

4. 1896 – Henri Becquerel
• Discovered Radioactivity
• Phosphorescence
o Uranium salts
• Nobel Prize in 1903

5. 1898 – Marie and Pierre
Curie
• First Radioactive
elements
o Radium and Polonium
• Polonium
o Half-life
Uraninite

6. Half-life

7. 1899/1900 Alpha, Beta,
Gamma

8. What is “radioactivity”?
• Emissions
o Not affected by temperature
o Could change color of glass
o Burn skin
o Create heat
• Rutherford and Soddy (1908)
o TRANSMUTATION of one element to another
• The atom is not an indestructible unit!

9. Types of Radiation
• Non-ionizing (low energy)
o Low frequency
• Ionizing (high energy)
o High frequency
• Activity!
o Label where you think non-ionizing and ionizing radiation are in
the spectrum
o categorize

10. ionizing
Non-ionizing

11. Nuclear Reactions

12. Nuclear Reactors

14. Importance