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### Nuclear Chemistry

Chapter 18

Quick Review

- Mass # Symbol
- Element Name or symbol – Mass #
- Parts of a Reaction
Reactants Products

Types of Radiation

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

Types of Radiation & Particles

- Positron emission or decay - 0+1e
- 2211Na 0+1e + 2210Ne
- Electron capture – beta particle in the reactants
- 20180Hg + 0-1e + 20179Au
- Neutron emission or decay– 10n
- 20984Po 10n + 20084Po
- Proton – 11H or 11p

Balancing Nuclear Equations

- Mass # and the atomic # totals must be the same for reactants and the products.
- 3919K 3517Cl + ___
- 20682Pb 0-1e + ___
- 23894Pu + ___ 42He + 23592U

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

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.

Sample Half-lives

- IsotopesHalf-Live
- Carbon – 14 5730 years
- Sodium – 24 15 hours
- Bismuth – 212 60.5 seconds
- Polonium – 215 0.0018 seconds
- Thorium – 230 75400 years
- Thorium – 234 24.1 days
- Uranium – 235 7.0 x 108 years
- Uranium – 238 4.46 x 109 years

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?

Half-life sample problems

- How many days will it take 50 grams of Radon – 222 (half-life of 3.82 days) to decay to 3.125 grams?

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?

Fission versus Fusion

- Fusion – combining two smaller nuclei into one heavier, more stable nucleus.
32He + 11H 42He + 01e

- Fission – splitting a large unstable nucleus into two nuclei with smaller mass numbers.
20984Po 12552Te + 8432Ge

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