1. Radioactivity

3. Radioactivity :
Is the spontaneous breaking up of unstable nuclei to give one or more type of radiation

4. Radioactivity Discovered by Henri Becquerel
Studying the effects of light on uranium salts
Found the uranium salt was giving off some type of radiation
Pierre and Marie Curie discovered polonium and radium
Were given the Nobel Prize for their work

5. Antoine Henri Becquerel
In 1896, while investigating uranium salts, Becquerel accidentally discovered radioactivity. Becquerel found that the photographic plates were fully exposed when in contact with radioactive salt.

6. Marie Curie
Developed a theory of radioactivity techniques for isolating radioactive isotopes, and discovered two new elements, polonium and radium

7. Pierre Curie
Pierre discovered nuclear energy, by identifying the continuous emission of heat from radium particles.
He also investigated the radiation emissions of radioactive substances, which lead to the discovery of alpha, beta and gamma radiation.

8. Types of Radiation
Alpha particles
Beta particles
Gamma rays

9. Alpha particles

10. He Alpha Particles Groups of 2 protons and 2 neutrons
(i.e. Same as the nucleus of a helium atom)
Represented as
Thrown out of the nucleus of a radioactive element as it changes to a more stable nucleus He 4 2

11. Alpha particles

12. Beta Particles - Are electrons
Neutron in an unstable atom changes into a proton and an electron
The electron is ejected from nucleus -
Beta Particle

13. Gamma Rays High energy electromagnetic radiation
An unstable nucleus emits gamma rays in order to lose surplus energy
Most dangerous of the three types

15. All three types of radiation detected using a Geiger-Muller Tube
Video!

16. + - None Type of radiation Nature Charge Example Alpha
Penetrating Power
Stopped by:
Example
Alpha
Helium nuclei (2protons + 2neutrons) +
Paper
Americium-241
Beta
Electrons -
Aluminium 5mm thick
Carbon-14
Gamma
Waves of high energy
None
Several cm of lead
Cobalt-60

17. Nuclear reactions
A nuclear reaction is a process that alters the composition, structure or energy of an atomic nucleus

18. Nuclear reactions
Alpha radiation
When an atom loses an alpha particle it changes into an atom two places before it on the periodic table.
The mass number decreases by 4
The atomic number decreases by 2

19. Nuclear reactions Radium-226  Radon-222 + alpha particle Ra  Rn + He
Alpha radiation
Radium-226  Radon alpha particle
Mass decreases by 4 [226222]
Atomic number decreases by 2 [8886]
226
222 4
Ra  Rn He 88 86 2

20. Nuclear reactions -
Beta radiation
When an atom loses a beta particle it changes into an atom one place after it on the periodic table.
The mass number stays the same.
Atomic number increases by 1

21. Nuclear reactions Carbon-14  Nitrogen-14 + beta particle C  N + e
Beta radiation
Carbon-14  Nitrogen-14 + beta particle
Mass number stays the same
Atomic number increases by 1 14 14
C  N e 6 7 -1

22. Chemical Reactions Nuclear Reactions
Involves electrons rather than the nucleus
Changes take place in the nucleus
No new element formed
New element formed
No release of nuclear radiation
Nuclear radiation released
Chemical bonds broken and formed
No bond breaking or formation

23. Half-Life
Scientists don’t fully understand why some nuclei spontaneously break up
Different radioactive isotopes break up at different rates
The rate of decay of an isotope is measured by its half-life.
The half-life of an element is the time taken for half of the nuclei in any given sample to decay.

24. Half-Life

25. A radioisotope (radionuclide) is an atom with an unstable nucleus.
Radioisotopes
A radioisotope (radionuclide) is an atom with an unstable nucleus.
Uses of radioisotopes
Medical– Cobalt-60 kill cancer
Smoke alarms- Americium- 241
Archaeological– Carbon-14 used in carbon dating
Industrial– radioisotope added to pipes to find leaks

26. Carbon dating Chernobyl: https://vimeo.com/112681885

27. Natural Radiation comes from
Sources in the earth that contain radioactive isotopes.
Sources from space in the form of cosmic rays
Sources in the atmosphere, particularly from radon gas that is released from the earth's crust.

28. Natural Radiation comes from
About 15% of background radiation comes from medical x-rays and nuclear medicine.
About 3% of background radiation comes from other man-made sources such as: nuclear testing, power plants, and smoke detectors.