Chapter 24 Applications of Nuclear Chemistry Read introduction page 776 Quick review of chapter 3 notes

Most elements and their isotopes found naturally are stable. Many radioactive elements and isotopes are man made. A few, such as uranium, are found naturally. The nuclei of unstable elements emit atomic particles to change the number of protons and eventually become a stable element.

Radioisotope – a radioactive isotope of an element Rubidium (Rb) has two naturally occurring isotopes. (Rb % and Rb %) Rb-85 is stable and Rb-87 is radioactive. It emits a beta particle and has a half life of 60 billion years. (show nuclear equation for this decay)

Half-life It is the time it take for ½ of a sample of a radioisotope to decay. See sample problem on page 780. Can also use the equation given below Amount left = (starting amount)(.5) (# of half-lives)

Carbon 14 Dating C-14 is produced by cosmic rays and atmospheric N- 14. (N-14 absorbs a neutron and ejects a proton) C-14 is oxidized in atmosphere to 14 CO 2. C-14 decays to N-14 by the emitting a beta particle. (show nuclear reaction) The C-14 concentration of C-14 in atmosphere is constant (The production and breakdown is a steady state process) C-14 has a half-life of 5730 years. When C-14 is taken up by plants the decay process is the same (good for dating once living things).

Nuclear Bombardment Reactions Alpha particles can be accelerated with particle accelerators and driven into the nucleus of an atom. This creates an unstable isotope which breaks down. Neutrons, because they are neutral) can be absorbed into a nucleus without being accelerated.

Biological Effects of Radiation Alpha particles are very weak and not harmful unless produced within the body. Beta particles can damage skin Gamma rays are very penetrating and harmful Dosimeter – used to measure the total radiation a person is exposed to in a given amount of time

Gamma rays (ionizing radiation) cuts through molecules producing ions and free radicals. Destruction of tissue – especially rapidly multiplying cells (lymph nodes) Marie Curie and her daughter both died of leukemia Can also result in genetic damage

Detection of Radiation Radiation also ionizes particles in the air and makes it more conductive to electricity. Smoke detectors rely on this and so do Geiger counters.

Beneficial Uses of Radioisotopes Radiotracers are placed in the body to track the movement and absorption of a particular element. (example I-131 to study thyroid) Radiation is often used for cancer treatment because tumors are runaway abnormal cell growth which are more susceptible to radiation. Radiation can extend the shelf life of many foods.

Radon – The Hidden Hazard Granite bedrock under much of the US contains small amounts of uranium-238. One of the decay products in Radon-222 which is a radioactive noble gas. This percolates up through the soil into basements. While in your lungs it changes into another elements which sticks to the lung and is the second leading cause of lung cancer.

Red – high risk orange – medium risk yellow – low risk

Nuclear Energy Nuclear fission is the splitting of large elements such as uranium into smaller ones. A nuclear reactor controls the U-235 fission reaction by controlling the number of neutrons with control rods.

Nuclear Accidents Critical mass – the mass of uranium necessary to create and runaway nuclear reaction (atomic bomb) The fuel rods in a nuclear reactor do not contain enough uranium to reach critical mass 1979 – Three Mile Island, Pennsylvania plant overheated 1986 – Chernobly, Ukraine plant had a graphite fire which resulted in meltdown

Nuclear Fusion Small atoms such as hydrogen adding to produce larger atoms. (the sun) An example is the hydrogen bomb. Requires very high temps (40 million C) We do not have the technology as yet to produce our electricity with a fusion reactor.

E = mc 2 All energy transformations result in a change of mass. The mass change in most situations is so small we cannot measure it. The energy given off in nuclear reactions is so great we can detect the change in mass. To use this equation E should be in Joules, mass in kilograms, and the speed of light (c) is 3 x 10 8 meters per second.

Iron sized elements are the most stable

Cold Fusion, the unfulfilled dream, may not be possible. Fusion could be a way out of our energy dilemma.