1. Nuclear Chemistry
7.5

2. The Discovery of Radiation
Wilhelm Roentgen – Discovered X rays in 1895.

3. The Discovery of Radiation
Henri Becquerrel – accidently discovered radioacitivity in 1896 when he left a uranium salt in a desk drawer on a photographic plate.
He hypothesized that the salt was g giving off some type of energy.

4. Marie and Pierre Curie – studied radioactivity in the late 1800s and early 1900s.
Radiation poisoning took Marie
Curies life.
She won the Nobel Prize in 1903
(They were super excited about it!)

5. Introduction to Nuclear Chemistry
The Nucleus – the protons and neutrons in the center of the atom that make up the positive charge.
Positive protons should repel from one another, why do they stay together in the nucleus?
The Strong Force – the force in the nucleus that causes protons and neutrons to attract to one another.

7. Typically in large or unstable nuclei the repulsion of the positive protons overcomes the strong force and nuclei decay.

8. Radioactivity Radioactivity – The process of nuclear decay
Decay depends on nuclear stability. If an isotope of an atom is radioactive it is called a radioisotope.

9. mass # atomic # Chemical Symbols C A chemical symbol looks like…
To find the number of neutrons , subtract the
atomic number from the mass number.
mass # 14 C
atomic # 6

10. Common Radioisotopes

11. Types of Radioactivity
Alpha particle – a particle of two protons and two neutrons that comes from a radioisotope. Often referred to as a Helium Nucleus.
Beta Particle – an electron emmitted from the nucleus of a radioisotope.
Gamma Rays – a form of radiation that is a powerful electromagnetic wave

13. Measuring Radiation
Geiger Counter – a device that measures radioactivity by producing an electric current when radiation is present.

14. Half-Life
Half life is the time required for half of a radioisotope’s nuclei to decay into its products.
For any radioisotope,
# of ½ lives
% Remaining
100% 1
50% 2
25% 3
12.5% 4
6.25% 5
3.125% 6
1.5625%

15. Half-Life
For example, suppose you have 10.0 grams of strontium – 90, which has a half life of 29 years. How much will be remaining after x number of years?  
You can use a table:
# of ½ lives
Time (Years)
Amount Remaining (g) 10 1 29 5 2 58
2.5 3 87
1.25 4
116
0.625

16. Half-Life

17. Nuclear Fusion and Nuclear Fission
A fusion reaction is a nuclear reaction that combines, or fuses, two smaller nuclei into a larger nucleus.
It is difficult to make fusion reactions occur because positively charged nuclei repel each other.
All stars, including the sun, generate energy through fusion.

18. Nuclear Fusion and Nuclear Fission
A fission reaction splits up a large nucleus into smaller pieces.
A fission reaction typically happens when a neutron hits a nucleus with enough energy to make the nucleus unstable.
Examples-atomic bomb

19. Uses of Radiation
Radioactive dating - Carbon - 14 used to determine the age of an object that was once alive.
Radiation to target cancer cells
X-rays
Medical tests using radioactive dyes, called tracers
Sterilizing equipment using radioactive rays
Smoke Detectors – alpha decay of americium 241

20. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons
May involve protons, neutrons, and electrons
Associated with small energy changes
Associated with large energy changes