1. Bellringer Please turn in your lab notebook to the cabinet
In your INB, explain Rutherford’s Gold Foil Experiment and the conclusions he drew from his findings

2. Ernest Rutherford’s Gold Foil Experiment - 1911
Alpha particles are helium nuclei - The alpha particles were fired at a thin sheet of gold foil
Particles that hit on the detecting screen (film) were recorded

3. Rutherford’s Findings
Most of the particles passed right through
A few particles were deflected
VERY FEW were greatly deflected
“Like howitzer shells bouncing off of tissue paper!”
Conclusions:
The nucleus is small
The nucleus is dense
The nucleus is positively charged

4. Nuclear Chemistry
The study of the structure of atomic nuclei and the changes they undergo.

5. As you may recall, isotopes are atoms of the same element that have different numbers of neutrons.
Isotopes of atoms with unstable nuclei are called radioisotopes

6. Radioactive Isotopes
Stable Isotopes -Atoms that do not release protons or neutrons from the nucleus and ARE NOT RADIOACTIVE.
Unstable Isotopes - Atoms that spontaneously release protons and neutrons from its nucleus. These isotopes ARE RADIOACTIVE.

7. Nuclear Reactions
Nuclear reactions are different from chemical reactions
Chemical Reactions
Mass is conserved (doesn’t change)
Small energy changes
No changes in the nuclei; involve ONLY valance electrons
Nuclear Reactions
Small changes in mass
Huge energy changes
protons, neutrons, electrons and gamma rays can be lost or gained

8. Types of Radiation
The effect of an electric field on three types of radiation is shown.
Positively charged alpha particles are deflected toward the negatively charged plate.

9. Figure 4.2: The penetrating power of radiation.
© 2003 John Wiley and Sons Publishers
Figure 4.2: The penetrating power of radiation.

10. Products of Natural Radioactivity
Mass
Particle* Symbol Charge Number Identity
Alpha 4 a Helium nucleus 2
Beta 0 b Electron -1
Gamma 0 g Proton of light
*Sometimes a stream of any of these types of particles is called a ray, as in gamma ray,

11. Figure 4.4: The components of α rays, β rays, and γ rays.
© 2003 John Wiley and Sons Publishers
Figure 4.4: The components of α rays, β rays, and γ rays.

12. Types of radioactive decay
alpha particle emission
loss of a helium nucleus.

14. Types of radioactive decay
Beta decay: nuclear changes that accompany the emission of a beta particle (CONVERTS A NEUTRON INTO A PROTON)

15. b particle emission

16. particle emission
Gamma rays are high-energy (short wavelength) electromagnetic radiation. They are denoted by the symbol.
As you can see from the symbol, both the subscript and superscript are zero.
Thus, the emission of gamma rays does not change the atomic number or mass number of a nucleus.
Gamma rays almost always accompany alpha and beta radiation, as they account for most of the energy loss that occurs as a nucleus decays.

17. Induced Nuclear Reactions
Scientists can also force ( = induce) nuclear reactions by smashing nuclei with alpha, beta and gamma radiation to make the nuclei unstable or

18. BALANCING NUCLEAR EQUATIONS
1. The sums of mass numbers (left superscripts) on each side must be equal.
2. The sums of atomic numbers or nuclear charges (left subscripts) on each side of the equation must be equal.
Examples:
238U 4He Th
214Pb 0 b Bi

19. Balancing Nuclear Equations
Complete the following nuclear equations:
At Bi + ?
Th b + ? -1
Tl b + ? 85 83
4He 2 90
231Pa 91 81
208Pb 82

20. Nuclear Reactions Two types: Fission = the splitting of nuclei
Fusion = the joining of nuclei (they fuse together)
Both reactions involve extremely large amounts of energy
Albert Einstein’s equation E = mc2 illustrates the energy found in even small amounts of matter

21. Nuclear Fission:
Is the splitting of one heavy nucleus into two or more smaller nuclei, as well as some sub-atomic particles and energy.
A heavy nucleus is usually unstable, due to many positive protons pushing apart.
When fission occurs:
Energy is produced.
More neutrons are given off.

22. Nuclear Fission Neutrons are used to make nuclei unstable
crash a neutral neutron into a nucleus to release energy

23. Fission produces a chain reaction

24. The fusion of hydrogen nuclei
Nuclear Fusion
joining of two light nuclei into one heavier nucleus.
In the core of the Sun, two hydrogen nuclei join under tremendous heat and pressure to form a helium nucleus.
When the helium atom is formed, huge amounts of energy are released.
The fusion of hydrogen nuclei

25. Scientists cannot yet find a safe, and manageable method to harness the energy of nuclear fusion.
“cold fusion” would occur at temperatures and pressures that could be controlled (but we haven’t figured out how to get it to happen)

26. Applications Medicine Agriculture Energy Chemotherapy Power pacemakers
Diagnostic tracers
Agriculture
Irradiate food
Pesticide
Energy
Fission
Fusion

27. Half-Life
The time required for the number of nuclides (# of protons + # neutrons) to reach half the original
Amount remaining of Radioactive Isotope:
N = N0 (1/2)n
N is remaining amount
N0 is the initial amount
n is number of half lives that have passed

28. Half-Life
Practice Problems # on page 872

29. A cancer patient receiving radiation therapy.
© 2003 John Wiley and Sons Publishers
Courtesy Kelley Culpepper/Transparencies, Inc.
A cancer patient receiving radiation therapy.

30. © 2003 John Wiley and Sons Publishers
Courtesy Scott Camazine/Photo Researchers
The world’s first atomic explosion, July 16, 1945 at Alamogordo, New Mexico.

31. © 2003 John Wiley and Sons Publishers
Courtesy Shigeo Hayashi
Remains of a building after the explosion of the uranium bomb at Hiroshima, August 6, 1945.

32. Cooling towers of a nuclear power plant.
© 2003 John Wiley and Sons Publishers
Courtesy David Bartruff/Corbis Images
Cooling towers of a nuclear power plant.

33. © 2003 John Wiley and Sons Publishers
Courtesy Sipa Press
The nuclear power plant at Chernobyl, after the accident of April 16, 1986.

34. © 2003 John Wiley and Sons Publishers
Courtesy Yucca Mountain Project
Construction of a tunnel that will be used for burial of radioactive wastes deep within Yucca Mountain, Nevada.

35. Disposal of radioactive wastes by burial in a shallow pit.
© 2003 John Wiley and Sons Publishers
Courtesy Matthew Neal McVay/Stone/Getty Images
Disposal of radioactive wastes by burial in a shallow pit.