1. Types of Reaction Types of Radiation Nuclear Equations
Radioactivity
Types of Reaction
Types of Radiation
Nuclear Equations

2. Reactions
Chemical reaction- atoms interact only through outer electrons
New substances are formed but the atoms identity remains the same.
Nuclear reaction- change the composition of an atom’s nucleus.

3. Reactions Chemical vs Nuclear Both nonrenewable
Nuclear produces far more energy then the same amount of chemical

4. Radioactivity Discovered in 1896
Spontaneous emission of radiation from an element- radioactive decay
Fundamental changes in an atom
Transmutation- One element changes into another

5. Nuclear Reaction Three different kinds of radiation can be emitted
Radioactive atoms emit radiation to try and stabilize their unstable nuclei
Three different kinds of radiation can be emitted
Alpha (α) particle
Beta (β) particle
Gamma (γ) ray

6. Alpha
2 protons and 2 neutrons
+2 charge
Identical to He-4

7. Alpha
Symbol

8. Alpha Low penetrating power Travel only short distances
Stopped by paper or clothing
Not much of a health risk

9. Beta
-1 charge
Mass = 0

10. Beta A neutron changes into a proton and an electron
The proton stays in the nucleus and the electron (beta particle) is propelled out of the nucleus at high speed.

11. Beta 100x more penetrating than alpha radiation
Able to penetrate through clothing and damage skin.

12. Beta
Symbol

13. Gamma Similar to x-rays Much more penetrating then alpha or beta
Able to penetrate deeply into solid materials

14. Gamma
Stopped by lead or concrete
Very dangerous

15. Gamma
Symbol

16. Characteristics of Alpha, Beta, and Gamma
Radiation Type
Symbol
Mass
(amu)
Charge
Alpha 4
Beta
1/1840
Gamma

17. What makes one atom radioactive and the other not?
The ratio of protons to neutrons that an atom contains

18. Radioactive?
Most stable nuclei have almost equal number of protons and neutrons.
Nuclei need increasingly more neutrons then protons to be stable.

19. Radioactive??
When the atomic number of an atom exceeds 83, the number of neutrons is insufficient.
So, all atoms with atomic # greater then 83 are radioactive.
Ex. Radium, Uranium, Francium

20. Radioactive??
Nuclei can also be unstable if they have too many neutrons.

21. How can protons exist so close to each other?
Nucleons- the protons and neutrons of a nucleus.
Electrostatic Repulsion- (like charges repel)
In order for the nucleus to stay together, there must be a attraction stronger then the repulsion.

22. Strong Nuclear Force
Holds together all protons and neutrons of a stable nucleus
Only works over short distances
Strong force > electrostatic repulsion

23. How does an atom not fall apart?
Strong force travels over short distances and repulsion forces can travel long distance, the forces balance each other out for nuclear stability.
If they are not balanced, the nucleus falls apart.

24. Radioactive Decay An atom emits one of the types of radiation.
Original nucleus decomposes, or decays, to form a new nucleus releasing radiation in the process.

25. Nuclear Reactions
Nuclear Fusion- two smaller nuclei fuse to form one larger nuclei. Lots of energy is released.
Occurs in stars

26. Nuclear Fission- Splitting a large nucleus into smaller nuclei
Nuclear Fission- Splitting a large nucleus into smaller nuclei. Lots of energy is produced (p654). Occurs in the nuclear reactors

27. Nuclear Equations
Alpha decay of an isotope of radium-228.

28. Nuclear Equations
Beta decay of Iodine-131.

29. Nuclear Equations Practice Alpha decay of Gold-185.
Beta decay of Sodium-24.

30. Nuclear Equations 94Be + 11H → _____ + 42He 3719K → _____ + 0+1e
24195Am + 42He → 210n + _____

31. Where does all the energy come from?
When protons and neutrons come together to form a nucleus energy is released.
Nucleons Nucleus + energy

32. Energy? Mass of any atom is LESS then the combined individual parts.
7 amu

33. Mass Defect
The difference in the mass of the whole vs the mass of the individuals.
E=mc2  mass can be converted to energy

34. Energy
Nuclear Binding Energy- energy released when the protons and neutrons come together.
The energy released is ENORMOUS compared to a chemical reaction.

35. Pros to nuclear power
Emits relatively low amounts of carbon dioxide (CO2): contribution of to global warming is therefore relatively little (less than one hundreth the Greenhouse Gases of Coal or Gas fired power stations)
This technology is readily
available.
Generates a high amount
of electrical energy

36. Cons of nuclear power Nonrenewable
The waste is extremely dangerous and it has to be carefully looked after for several thousand years
High risks: Despite high standards, accidents can still happen. The consequences of an
accident can be absolutely
devastating.
Nonrenewable

37. Nuclear Power Plants
Today’s power plants produce energy through fission chain reactions.
Fusion reactions are cleaner and safer but, with our present technology, it takes more power to do fusion then it produces.

38. Nuclear Power Plants

39. Nuclear incidents 3-mile Island 1979
Partial nuclear meltdown in Pennsylvania

40. Chernobyl- April 26,1986

41. Time Line
26 April 1986, 1:23:00: A test of the cooling system begins in unit no. 4 of the Chernobyl power plant
26 April 1986, 1:23:40: The emergency shutdown fails.
26 April 1986, 1:23:44: The reactor in unit no. 4 runs out of control and explodes.
26 April 1986: In the town of Pripyat, 3 km away, there are people, including children enjoying the first warm Sunday of the spring.

42. 27 April 1986: The inhabitants of the Pripyat power plant settlement are evacuated.
28 April 1986, 21:00: The Soviet news agency Tass announces that there has been an accident at the Chernobyl nuclear power station and that there have been casualties. An investigative committee is established.
29 April 1986: The accident at Chernobyl is first reported in German newscasts.

43. 26 April to 4 May 1986: Most of the radiation is released in the first ten days.
27 April to 5 May 1986: About 1800 helicopter flights deposit around 5000 tonnes of extinguishing materials such as sand and lead onto the burning reactor.

44. Radiation Spread
The U.S.S.R. was silent about the accident until after it had been detected by its neighbors to the north.

45. Fukushima 2011 Japan Largest disaster since Chernobyl
3 reactors experienced meltdowns before being brought under control.

47. Radioisotopes
Elements have one or more isotopes that are unstable and decay to produce other elements

48. Half-Life The time it takes for one half of a radioisotope to decay.
Half-lives
Rubidium billion years
Carbon years

49. Half-life
Ex. The half-life of mercury-195 is 31 hours. If you start with a 5.00g of mercury-195, how much of it will still be present after 93 hours?

50. Half-life
Try: Gold-191 has a half-life of 12.4 hours. What mass of this isotope would remain after 49.6 hours if you started with a 7.50g sample of Au-191?

51. Carbon dating
Process of determining the age of an object by measuring the amount of carbon-14 remaining in the object.

52. Nuclear Use Medical: PET Scan Smoke Detector
Smoke Detector
contains an
Radioisotope:
americium-241.