1. Nuclear Chemistry
Chapter 18

2. Quick Review Mass # Symbol Element Name or symbol – Mass #
Parts of a Reaction
Reactants  Products

3. Types of Radiation Alpha emission or decay (a) –helium atom 42He
23892U  42He Th
Beta emission or decay (b)– 0-1e in the products
23490Th  23491Pa + 0-1e
Gamma emission or decay (g) - 00g
23892U  42He Th + 00g

4. Types of Radiation & Particles
Positron emission or decay e
2211Na  0+1e Ne
Electron capture – beta particle in the reactants
20180Hg e  20179Au
Neutron emission or decay– 10n
20984Po  10n Po
Proton – 11H or 11p

5. Balancing Nuclear Equations
Mass # and the atomic # totals must be the same for reactants and the products.
3919K  3517Cl + ___
20682Pb  0-1e + ___
23894Pu + ___ 42He U

6. Writing Balanced Nuclear Equations
Alpha decay of Cu-68
Gamma emission of Thorium-235
Positron emission of P-18
Astatine-210 releasing 3 neutrons
Electron capture of Ti-45

7. Half-Life and Nuclear Stability
Radioactive isotopes or nuclides all decay because they are unstable, some just breakdown much faster than others
Half-life – amount of time for half of the original sample to decay
For two samples of the same isotope, regardless of the sample size, after one half- life, only half of the original amount of sample remains.

8. Sample Half-lives Isotopes Half-Live Carbon – 14 5730 years
Sodium – hours
Bismuth – seconds
Polonium – seconds
Thorium – years
Thorium – days
Uranium – x 108 years
Uranium – x 109 years

9. Half-life sample problems
Barium – 139 has a half-life of 86 minutes. If you originally have a 10 gram sample of Barium-139, how much will be left after 258 minutes?

10. Half-life sample problems
How many days will it take 50 grams of Radon – 222 (half-life of 3.82 days) to decay to grams?

11. Half-life sample problems
If a sample of Cesium-135 decays from 10 grams to 2.5 grams over a period of 84 days, what is the half-life of Cesium-135?

12. Predicting radiation types from Reaction Products
238U  234Th  234Pa  234U
α β β
234U  230Th  226Ra  222Rn  218Po  214Pb
α α α α α
214Pb 214Bi 214Po 210Pb 210Bi 210Po206Pb
β β α β β α

13. Scientists who shaped Nuclear Chemistry
Henri Becquerel Discovered Natural
Radioactivity - Nobel Prize (physics) 1903
Wilhem Roentgen Discovered X- rays
(1895) - Nobel Prize (physics) 1901
Marie (Sklowdowska) Curie 1867 – 1934 Discovered
Radium and Polonium - (2) Nobel Prizes (physics)
1903, Chemistry (1911) – first woman to teach at the
Sorbonne in its 650 yr history, first person to receive
two Nobel prizes, only person to receive 2 Nobels in
Sciences

14. Medical Applications of Nuclear Chem.
Cancer Radiation Treatment
Computer Imaging techniques
Radiocarbon dating
Smoke detectors
Food irradiation
Radioactive tracers – Iodine 131 used to treat thyroid illnesses and Thallium -201 can be used determine the damage done to someone’s heart by a heart attack

15. Scientists who shaped Nuclear Chemistry
Pierre Curie Nobel Prize (physics) 1903
Ernest Rutherford Demonstrated the existence of the nucleus Nobel Prize (chemistry) 1908

16. Fission
Nuclear fission was discovered in late 1930’s when U-235 was bombarded with neutrons and observed to split into two lighter elements.
10n U  9236Kr Ba + 310n
Energy from combustion of 1 mole of U-235 produces 26 million times as much energy as the combustion of 1 mole of methane.

17. Fission
The neutrons are produced from fission reactions, will then react with other radioactive atoms, which will produce more neutrons and so on, potentially creating an uncontrollable chain reaction.

18. Critical State of a Fission Reaction
If reaction produces < 1 neutron on average, the nuclear fission stops over time.
If reaction produces exactly 1 neutron for each fission, the process is self-sustaining and is said to be critical.
If reaction produces > 1 neutron from each fission than the process can get out of control very quickly and cause a violent explosion.

19. Critical Sate of a Fission Reaction
Critical mass = mass of fissionable material needed to keep fission reaction going, but at a safe level.
Hiroshima and Nagasaki bombs in 1945 were fission bombs where two subcritical masses were combined and have an extremely rapid fission reaction that causes a huge explosion.

20. Sample fission reaction

21. Nuclear Fusion
Fusion – combining two smaller nuclei into one heavier, more stable nucleus.
32He + 11H  42He + 01e
Fusion reaction produce more energy than fission reactions.
Fusion reactions are most commonly seen in stars.

22. Nuclear Fusion
We have many potential sources for fusion reactions, but the problem lies in trying to slam two positively charged nuclei together with enough force to make them combine.
It is thought that the temperature must be over 40 million Kelvin for this to occur, which is where the speed of the particles could potentially overcome the repulsive forces.

23. Sample fusion reaction

24. Effects of Radiation
Somatic damage – done to the organism itself, resulting in either sickness or death.
Effect of somatic damage may be immediate or take years to show their effects, such as radiation treatment for cancer patients.
Genetic damage – damages cells which can be passed on to afflict offspring of initially effecting organism.

25. Effects of Radiation
Energy of radiation – higher energy = more damage (big surprise)
Penetrating ability of the radiation – gamma particles are high penetrating, beta can penetrate 1 cm and alpha particles can be stopped by the skin.