1. Nuclear Chemistry
Bravo – 15,000 kilotons

2. Energy = (mass)x(speed of light)2
Nuclear Power
What is radioactivity? Any process where the nucleus emits particles of energy. When the strong nuclear force is not large enough to hold the nucleus together tightly, the nucleus becomes radioactive
Nuclear reactions involve the nucleus instead of the electrons as in a regular chemical reaction.
The instability of the nucleus of a radioactive element causes the # of protons and neutrons to change.
Some of the mass can be converted into a tremendous amount of energy shown by a very famous equation:
E=mc2
Energy = (mass)x(speed of light)2

3. Neutrons add strong nuclear force without repelling the protons.
Over 83 protons and the nucleus will undergo radioactive decay.

4. Nuclear Chemistry radioactive
1. An isotope with an unstable nucleus is said to be _________________________.
2. In a nuclear reaction, a nucleus will gain or lose ___________________ and/or _________________.
3. An atom with _________ or more protons is radioactive.
protons
neutrons 84

5. Nuclear Chemistry History
In 1896, Henri Becquerel first discovered radiation and radioactive decay by accident using uranium and photographic film.

6. Also in 1896, Marie Curie and Pierre Curie found that only two elements known at the time, uranium and thorium, were radioactive. In 1898, the Curies discovered two new radioactive elements, polonium and radium.

7. Bequerel along with Marie and Pierre Curie were awarded the Nobel prize in Physics in 1903, and Marie again received a Nobel prize in 1911 (one of four people ever to get two prizes, first woman Nobel prize).
The discovery dealt a deathblow the Dalton’s theory of indivisible atoms.
Marie Curie died from leukemia caused by her long-term exposure to radiation.

8. Applications of Nuclear Radiation
Radioactive Dating
half-life measurements of radioactive elements are used to determine the age of an object
decay rate indicates amount of radioactive material
Example: 14C - up to 40,000 years 238U and 40K - over 300,000 years

9. Applications of Nuclear Radiation
Radioactive Tracers
In medicine:
absorbed by specific organs
and used to diagnose diseases
In agriculture:
study plant growth,
photosynthesis

10. Applications of Nuclear Radiation
Nuclear Medicine
Radiation Treatment
larger doses are used to kill cancerous cells in targeted organs
internal or external radiation source,
usually Cobalt-60

11. Types of Radiation

12. Types of Radiation

13. Alpha Radiation
Alpha decay is limited to VERY large, nuclei such as those in heavy metals.

14. Beta Radiation
Beta decay converts a neutron into a proton.

15. Penetrating Power of Radiation and Shielding Radiation (How to stop radiation from killing you)
Which type of radiation is the most penetrating? gamma rays
Which type of radiation do you think is most dangerous? gamma rays
Sun glasses have UVA and UVB protection.
The UV-A stand for ultra violet alpha particles and the UV-B stands for ultra violet beta particles.
Almost all sunglasses offer 100% UVA protection. Be sure to get 100% UVB protection as well.

16. More Nuclear Reactions
A. Nuclear Fission – the splitting of a nucleus into smaller fragments (the splitting is caused by bombarding the nucleus with neutrons). This process releases enormous amounts of energy.
A nuclear chain reaction is a reaction in which the material that starts the reaction (neutron) is also one of the products and can be used to start another reaction.

17. B. Fission chain reaction - self-propagating reaction
critical mass - mass required to sustain a chain reaction

18. C. Nuclear Power Plants
Nuclear Reactors use controlled fission chain reactions to produce energy or radioactive nuclides.

19. C. Nuclear Power
a. shielding – radiation absorbing material that is used to decrease exposure to radiation.

20. C. Nuclear Power
b. fuel – uranium is most often used

21. C. Nuclear Power
Steam
e. coolant – water acts as a coolant and transports heat between the reaction and the steam turbines to produce electric current

22. C. Nuclear Power
Nuclear Power Plants produce a great deal of energy, the current problems with nuclear power plants include environmental requirements, safety of operation, plant construction costs, and storage and disposal of spent fuel and radioactive waste.

23. D. Atomic Bomb
chemical explosion is used to form a critical mass of 235U or 239Pu
fission develops
into an uncontrolled
chain reaction

24. Fusion
A. Combining of two nuclei to form one nucleus of larger mass, usually very small atoms of hydrogen and helium are used. B. Thermonuclear reaction – requires temp of 40,000,000 K to sustain 1 g of fusion fuel = 20 tons of coal

25. Fusion
C. Sun/Stars – four hydrogen nuclei combine at extremely high temperatures and pressures to form a helium nucleus – this is a fusion reaction.

26. B. Fusion
Hydrogen Bomb- uncontrolled fusion reactions of hydrogen are the source of energy for the hydrogen bomb. Hydrogen bombs generate a great deal more of energy then an atomic bomb.

27. Nuclear Fusion + + + Sun Energy Four hydrogen nuclei (protons)
Two beta
particles
(electrons)
One
helium
nucleus

28. B. Fusion
Fusion as a Source of Energy: Fusion reactions generate a great deal more energy and their products are less harmful then fission reactions.
Research is being done to try to use fusion instead of fission, there are a few problems: the temperature required is so high no known material can withstand the temperature.

29. TYPES OF NUCLEAR ENERGY Fission vs. Fusion
Different
Alike
Different
Change
Nucleus of
Atoms
Split
large atoms
Using U-235
Fuse small atoms
2H2 He
Topic
Topic
Radioactive
waste
(long half-life)
Create
Large Amounts
of Energy
E = mc2 NO
Radioactive
Waste so is
safe
Fusion
Fission
Nuclear
Power
Plants
Transmutation
of Elements
Occurs
Very High
Temperatures
~5,000,000 oC
(ON THE SUN)

30. Nuclear Power Plants
map: Nuclear Energy Institute

31. Nuclear Isotope Symbols
Element
symbol
Mass number
(p+ + no)
Atomic number
(number of p+)

32. Nuclear Chemistry Reactions
In alpha decay the atomic number will decrease by 2 and the mass number will decrease by 4 (helium nucleus)
Example:
The alpha decay of iridium-174

33. Nuclear Chemistry Reactions
In beta decay the atomic number will increase by 1 and the mass number will stay the same. (electron emmision)
Example:
The beta decay of platinum-199

34. Nuclear Chemistry Reactions
Neon 20 a B B a a a a a B B B a B a
Silicon 30

35. Half-Life Problems
The half-life of an isotope refers to the time it takes for one-half of the sample to decay.
Example: If we start with 100 g of a radioactive substance whose half-life is 15 days, after 15 days 50 g of the substance will remain. After 30 days, 25 g will remain, and after 45 days, 12.5 g remains, and so on.

36. Half-Life Problems
Example: A radioactive substance has a half-life of 20 minutes. If we begin with a 500 g sample, how much of the original sample remains after two hours?
Explanation
The easiest way to attack these questions is to start with the original amount of the sample, then draw arrows representing each half-life. Two hours is 120 minutes, so that’s six half-lives. At the end of the stated time period, 7.8 g remains.
500 g g g g g g g

37. 64 g (13 hours later)432g (13 hours later)416g (13 hours later) 48g
Learning Check!
The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 39 hours?
64 g (13 hours later)432g (13 hours later)416g (13 hours later) 48g
After 39 hours 8 grams of I-123 will be left

38. Half-life of Radiation
Initial amount
of radioisotope
Number of half-lives
Radioisotope remaining (%)
100 50 25
12.5
After 1 half-life
After 2 half-lives
After 3 half-lives
t1/2
t1/2
t1/2