1. Nuclear Chemistry Review & Calculations
Ms. Sipe

2. Nuclear Chemistry Reactions in the nuclei of atoms Nuclear reactions
Changes in the nuclei
Involve the emission of energy- rays or particles
Not affected by temperature, pressure , or catalysts like regular chemical reactions
In chemical rxns bonds break and rearrange to form new substance (reactivity based on what subatomic particle?)

3. Nuclear Chemistry Types of nuclear reactions
Fusion- combining of nuclei, releases a lot of energy
Stars and the sun
Fission- splitting of nuclei into smaller nuclei
Radioactive Decay or radioactivity
Reactions begin with unstable isotopes called radioisotopes that undergo change to become stable

4. Nuclear Fusion
The energy emitted by the sun results from nuclear fusion.
Fusion occurs when nuclei combine to produce a nucleus of greater mass.
In solar fusion, hydrogen nuclei (protons) fuse to make helium nuclei. A LOT OF ENERGY PRODUCED!
The reaction also produces two positrons.

5. Nuclear Fission More neutrons are released by the fission.
The figure below shows how uranium-235 breaks into two smaller fragments of roughly the same size when struck by a slow-moving neutron. U
Uranium-235
(fissionable)
235 92
Uranium-236
(very unstable)
236 Ba
Barium-142
142 56 Kr
Krypton-91 91 36
3 n 1
Neutron
More neutrons are released by the fission.
These neutrons strike the nuclei of other uranium-235 atoms, which cause chain reactions.

6. Recap: Fusion vs Fission
Combining 2 light nuclei to form a heavier nucleus
Requires high T & P
Powers stars & sun
Splitting a heavy nucleus into 2 nuclei with smaller mass #
Radioactive decay (w/o neutron)

7. Types of Nuclear Emissions/Radiation
Characteristics of Some Types of Radiation
Type
Consists of
Symbol
Charge
Mass (amu)
Common source
Penetrating power
Alpha radiation
Alpha particles (helium nuclei)
or a 2+ 4
Radium-226
Low (0.05 mm body tissue)
Beta radiation
Beta particles (electrons)
or b 1–
1/1837 ~ 0
Carbon- 14
Moderate
(4 mm body tissue)
Gamma radiation
High-energy electromagnetic radiation g
Cobalt-60
Very high (penetrates body easily)

8. Mass # decreases by 4 & Atomic # decreases by 2
Alpha Radiation U
238 92
Uranium-238
Th +
234 90
Thorium-234
He (a emission) 4 2
Alpha particle
Radioactive
decay
Mass # decreases by 4 & Atomic # decreases by 2

9. Carbon-14 (radioactive)
Beta Radiation C 14 6
Carbon-14 (radioactive)
N + 7
Nitrogen-14 (stable)
e (b emission) –1
Beta particle → n 1
Neutron
p +
Proton e –1
Electron
(beta particle) →
An electron resulting from the breaking apart of neutrons in an atom # of protons increases while #of neutrons decreases. Same Mass #; Atomic # increases by one

10. Gamma Radiation Ra + Th He + g → Pa + Th e + g →
226 88
Radium-226 Th
230 90
Thorium-230
He + g 4 2
Alpha particle
Gamma ray →
Pa +
234 91
Protactinium-234 Th 90
Thorium-234
e + g –1
Beta particle
Gamma ray →
Nuclei often emit gamma rays along with alpha or beta particles during radioactive decay.
Gramma ray – no mass/no electric charge - Does not alter the atomic number or mass number of an atom.

11. Balancing Nuclear Equations
U-238 alpha decay- Helium particle emitted 23892U  ? Th Na -24 beta decay- electron emitted 2411Na  ? Mg

12. Balancing Nuclear Equations
U-238 alpha decay- Helium particle emitted 23892U  42He Th Na -24 beta decay- electron emitted 2411Na  0-1e Mg

13. Nuclear Chemistry Application of Radioisotopes Smoke Detectors
Food Irradiation
Archaeological Dating
Medical Uses
Nuclear Power
Nuclear Weapons

14. Applications of Nuclear Reactions
Nuclear power and Nuclear weapons Most common nuclear fuel: Uranium-235, Plutonium-239 Difference btw power & weapon Power – can control E release & convert to heat Weapon – uncontrolled release of E

15. Power
Nuclear energy – Fr ~80%, US 20%, Japan 35%, Germany – 30%
Weapon
Fission weapons – Atomic bombs (A-bomb)
Fusion weapons – Hydrogen bombs (H-bomb)
Manhattan Project WWII
Submarines – that use nuclear energy stay longer underwater

16. A Few Pros and Cons No more need for oil Not using fossil fuel
Fission > energy compared to gasoline
Will have unlimited amounts of energy (esp if fusion works; sun)
No need for us to depend on other countries
Hard to control
Nuclear waste
Pollution
Radiation
Nuclear reactor – away from large population, waterways, earthquake zones
Japan reactor explosion – then cooling system fails so further explosion or leak of radioactive material can occur
Nuclear reactor overheating – explode like a nuclear weapon
Nuclear weapon – destructive potential

17. A half-life (t½) is the time required for one-half of the nuclei in a radioisotope sample to decay to products.
After each half-life, half of the original radioactive atoms have decayed into atoms of a new element.

18. Half-Lives of Some Naturally Occurring Radioisotopes
Half-Life
Comparing Half-Lives
Half-lives can be as short as a second or as long as billions of years.
Half-Lives of Some Naturally Occurring Radioisotopes
Isotope
Half-life
Radiation emitted
Carbon-14
5.73 × 103 years b
Potassium-40
1.25 × 109 years
b, g
Radon-222
3.8 days a
Radium-226
1.6 × 103 years
a, g
Thorium-234
24.1 days
Uranium-235
7.0 × 108 years
Uranium-238
4.5 × 109 years

19. Half-Life Comparing Half-Lives
Uranium-238 decays through a complex series of unstable isotopes to the stable isotope lead-206.
The age of uranium-containing minerals can be estimated by measuring the ratio of uranium-238 to lead-206.
Because the half-life of uranium-238 is 4.5 × 109 years, it is possible to use its half-life to date rocks as old as the solar system.

20. Half Life Calculations
The half-life of beryllium-11 is seconds. Let's say you start with 16 grams of 11Be. After 13.81s, you have 8 grams of that isotope left (the rest will have decayed to something else). After another 13.81s, you have 4 grams left; seconds more, and you have 2 grams left……so after 3 half lives berllium-11 decayed from 16g to 2 g. In chemistry, you set up tables like this:
Time
Amount remaining
0 s
16 grams
13.81 s
8 grams
27.62 s
4 grams
41.43 s
2 grams

21. Practice Problem…
In a particular bone sample, you have 80g of a parent and 560g of a daughter isotope. The half life of the sample is 100 years. How old is the bone? 560g + 80g = 640 g for the original parent 640  320  160  80 equals 3 half lives (3)(100 yrs) = 300 years old Now, you try some…

22. Closure:
Germany said it would close all of its 17 nuclear reactors by 2022, a sharp policy reversal that will make it the first major economy to quit atomic power in the wake of the nuclear crisis in Japan. Do you think USA should do the same?
Provide 3 reasons to support your answer