1. Nuclear Chemistry
Bravo – 15,000 kilotons

2. Nuclear Chemistry
Title a new section in your notebook called Nuclear Chemistry
Also, get a periodic table in front of you.

3. Radioactive Decay
Radioactive decay is the spontaneous breakdown of an unstable atomic nucleus. It releases alpha, beta, and/or gamma radiation.
Very large atoms (atomic # 84 and up) are radioactive. Find these now on your periodic table.
Smaller atoms with an unstable number of protons and neutrons can be radioactive too.
Atoms will be unstable if they do not have the “right” ratio of protons : neutrons.

4. Draw a nucleus of Mg and U

5. Strong Nuclear Force is an attractive force that holds heavy particles together in the nucleus, overcoming the electrostatic repulsion from positively charged protons.
This strong force keeps the nucleus from falling apart.
Only works at very close distances!!

6. Marie Curie
Isolated the radioactive elements Po, Ra and U
Coined the term “radioactivity”
Both Marie and her daughter Irene died of leukemia as a result of prolonged exposure to radioactive decay

7. Radiation is the penetrating rays and particles emitted by a radioactive source.
Radioactivity is the
process by which
materials give off such
rays.

8. Ernest Rutherford
Used a radioactive substance and charged plates to characterize the different types of radioactivity and the types of particles released.
Three Main Types of radiation: Alpha, Beta, and Gamma

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

10. Alpha Particle (α)
Alpha particles are composed of the same particles as the nucleus of a helium–4 atom.
Have a 2+ charge
They are relatively large and slow moving (compared to speed of light)
It has relatively poor penetrating power; generally they are not dangerous unless ingested.

11. Beta Radiation
Beta decay converts a neutron into a proton & ejects a beta particle (an electron).

12. Beta particle (β):
Beta particles are essentially the same as an electron, they have very little mass and a charge of -1.
Beta particles are created when a neutron in the nucleus ejects an electron and becomes a proton.
Because of their low mass and moderate speed, they have a moderate level of penetration and damage.

13. Gamma Radiation (γ): On the electromagnetic spectrum Has no charge
No mass, but travels at the speed of light
Very high energy, high frequency radiation, like a super-powered ray of light or X-ray (just with much more energy)
Excellent penetration (lead/concrete suit!)
Very dangerous and damaging (has the most energy)
Gamma radiation is a byproduct of both beta and alpha decay

14. What can protect us?

15. Alpha Particle Emission Beta Particle Emission
Gamma Ray Emission
Symbol or
Mass
Heavy
Light
No Mass
How it changes the nucleus
Decreases the mass number by 4
Decreases the atomic number by 2
Converts a neutron into a proton (Mass # doesn’t change)
Increases atomic number by 1
No change to the nucleus
Penetration
Low
Medium
High
Protection provided by…
Skin; paper
Clothing; wood
Lead; super thick concrete
Danger

16. Nuclear reactions are far greater than ordinary chemical reactions

17. Radioisotopes and Half Life
- A radioisotope is an isotope which will undergo radioactive decay over time due to an unstable number of protons and neutrons in its nucleus. (It has too many or too few neutrons.)
Most elements have at least one naturally occurring radioisotope. There is radioactive decay happening inside of you right now.
Most naturally occurring decay is at such low levels that it is harmless.
Some very unstable nuclei can decay very quickly, others will decay much more slowly.

18. A half life of a radioactive isotope is the time it takes for ½ of a sample of that isotope to decay. Knowing the half lives of different isotopes can be used to determine the age of an object.
Strontium-90 has a ½ life of 28.8 years
Carbon-14 is an especially useful isotope for dating wooden artifacts or the remains of an organism.
Carbon-14 has a ½ life of 5,730 years, making it useful for dating objects up to 60,000 years old.

19. Half-life Practice Sample Question 1:
The ½ life of mercury-195 is 31 hours. If you begin with a 5.00 g sample of 195Hg, how much of it will be present after 93 hours?

20. Sample Question 2:
Cobalt-60 has a half-life of 5.25 years? If you started with 20.0 grams of Cobalt-60, how much would remain after 10.5 years?

21. Sample Question 3:
A 64.0 g sample of germanium-66 is left undisturbed for 25 hours. At this time, only 2.0 g of germanium-66 remained. How many half lives did germanium-66 undergo?

22. Where are the transuranic elements on the periodic table?
“trans” prefix means “after”
Uranic looks like what element?
= “after” Uranium
So transactinide elements would be where?

23. In a nuclear fission reaction, a large nucleus is split into two smaller nuclei of approximately equal mass.
During nuclear fission a very small amount of mass is “lost” as it is converted into an enormous amount of energy!

24. Fission
Fission - Splitting a heavy nucleus into two nuclei with smaller mass numbers.

25. In a chain reaction the neutrons produced at the end of one nuclear fission reaction are used to initiate a successive reaction. This can lead to a geometric expansion of fission reactions.
Atomic bombs are designed to create a “runaway” chain reaction which will use up all of the uranium present and create an incredibly powerful explosion.
Nuclear reactor plants do not contain enough 235U to sustain a chain reaction. The major “meltdown” concern is the uncontrolled release of the radioactive waste produced during these reactions!

26. In a nuclear fusion reaction, two lighter nuclei are fused together to form a heavier nucleus.
This reaction also causes a small amount of mass to be “lost” as it is converted into a tremendous amount of energy.
Fusion is difficult to achieve due to the electrostatic repulsion of like-charged electron clouds and then by the repulsion of the like-charged protons in the nucleus.
Stars use fusion reactions as fuel. They overcome the repulsion problem with a combination of tremendous heat and gravitational force to force the nuclei together!
Cold Fusion research is aimed at finding a viable method for using fusion as a pollution free fuel source. It has not yet been successful.

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

28. Types of Radioactive Decay
alpha production (a, He): helium nucleus
beta production (b, e):
gamma ray production (g):

29. Nuclear Stability
Decay will occur in such a way as to return a nucleus to the band (line) of stability.

30. Deuterium – Tritium Fusion Reaction
Fusion - Combining two light nuclei to form a heavier, more stable nucleus.

31. Albert Einstein used the formula: E=mc2 to describe the possibility for the interchange between energy and mass.
This formula shows that an absolutely enormous amount of energy can be derived from a small amount of matter!!
E = mc2
E = energy
m = mass defect (mass lost during fission or fusion)
c = speed of light (3.0 x 108 m/s)

32. Energy and Mass
Nuclear changes occur with small but measurable losses of mass. The lost mass is called the mass defect, and is converted to energy according to Einstein’s equation:
DE = Dmc2
Dm = mass defect
DE = change in energy
c = speed of light
Because c2 is so large, even small amounts of mass are converted to enormous amount of energy.

34. A Fission Reactor

35. Summary of Nuclear Chemistry
Take your knowledge and create a beautiful poster.
Include all CA standards on poster.
Winning lab group wins lunch with me.

36. CA Standards
Students know protons and neutrons in the nucleus are held together by nuclear forces that overcome the electromagnetic repulsion between the protons.
Students know the energy release per gram of material is much larger in nuclear fusion or fission reactions than in chemical reactions. The change in mass (calculated by E = mc2) is small but significant in nuclear reactions.

37. CA Standards
Students know the three most common forms of radioactive decay (alpha, beta, and gamma) and know how the nucleus changes in each type of decay.
Students know alpha, beta, and gamma radiation produce different amounts and kinds of damage in matter and have different penetrations.
Students know some naturally occurring isotopes of elements are radioactive, as are isotopes formed in nuclear reactions.