Nuclear chemistry

Nuclear chemistry is a subfield of chemistry dealing with radioactivity, nuclear processes and nuclear properties. It may be divided into the following main categories:

Radiochemistry

Radiochemistry is the chemistry of radioactive materials, in radiochemistry it is oftein the case that the radioactive isotopes of elements are used to study the properties and chemical reactions of ordinary non radioactive (oftein within radioachemistry the absence of radioactivity leads to a substance being described as being inactive as the isotopes are stable). An example of a biological use of radiochemistry would be the study of DNA using radioactive phosphorus-32.

Radiation chemistry

Radiation chemistry is the study of the chemical effects of radiation on matter, this is very different to radiochemistry as no radioactivity needs to be present in the material which is being chemically changed as a result of the radiation. An example of radiation chemistry would be the conversion of water into hydrogen gas and hydrogen peroxide.

Study of nuclear reactions

A combination of raiochemistry and radiation chemistry is used to assist in the study of nuclear reactions such as fission and fusion — see also nuclear physics. For instance some of the early evidence for nuclear fission was the formation of a shortlived radioisotope of barium { Both Ba-139 (half life 83 minutes) and Ba-140 (half life 12.8 days) are major fission products of uranium} which was isolated from neutron irradated uranium, at the time it was thought that this was a new radium isotope as it was the standard radiochemical practise at the time to use a barium sulphate carrier percipitate as a means of assisting in the isolation of radium.[1] For more details see the work of Otto Hahn.

Lise Meitner and O.R. Frisch, Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction, Nature, 143, 239-240, (Feb. 11, 1939)[2]

The nuclear fuel cycle

The chemistry associated with any part of the nuclear fuel cycle, eg advanced reprocessing.

Spinout areas

Some methods which were first developed within nuclear chemistry and physics have become so widly used within chemistry and other physical sciences that they may be best thought of as not being part of normal nuclear chemistry.

Isotopic chemistry

The area of Isotopic chemistry could be included in this subtopic, but due to the use of the isotope effect to investigate chemical mechanisms and the use of cosmogenic isotopes and long lived unstable isotopes in geology it is best to consider much of isotopic chemistry as being separate from nuclear chemistry.

Kinetics (use within mechanistic chemistry)

The mechanisms of chemical reactions can be investigated by observing the effect upon the kinetics of making an isotopic modification of a substrate in a reaction. This is now a standard method in organic chemistry so it best that the isotope effect is considered within the contex of organic chemistry. In short the replacement of normal hydrogens (protons) within a chemical compound with deuterium causes the rate of molecular vibration (C-H, N-H and O-H bonds show this) to decrease, this then can lead to a decrease in the reaction rate if the rate determining step involves the breaking of a bond between hydrogen and another atom, hence if upon replacement of protons for deuteriums the reaction changes in rate it is reasonable to assume that the breaking of the bond to hydrogen is part of the step which determines the rate.

Uses within geology, biology and forensic science

Cosmogenic isotopes are formed by the interaction of cosmic rays with the nucleus of an atom. These can be used for dating purposes and for use as natural tracers. In addition by careful measurement of some ratios of stable isotopes it is possible to obtain new insights into the origin of bullets, ages of ice samples, ages of rocks, and the diet of a person can be identified from a hair or other tissue sample. see Isotope geochemistry and Isotopic signature for further deatils.

Nuclear magnetic resonance

Spectrscopy

NMR spectroscopy uses the net spin of nuclei in a substances upon energy absorption, and is used to identify molecules. This has now become a standard spectrscopic tool within synthetic chemistry, one of the main uses of NMR is as a means of determining the bond connectivity within an organic molecule.

Imaging

NMR imaging also uses the net spin of nuclei (commonly protons) as a means of imaging. This is commonly used within medicine becuase it can provide detailed images of the inside or a person without inflicting any radiation dose upon them. Commonly in a medical setting NMR is known as "Magnetic resonance imaging as the word nuclear has such a negative conotation that many persons are fearful of anything nuclear.

Text books

Radiochemistry and Nuclear Chemistry

• Choppin, Liljenenzin and Rydberg
• ISBN -0750674636, Butterworth-Heinemann, 2002

Description: Very comprenhensive textbook on the subject.

Radioactivity, Ionizing radiation and Nuclear Energy

• Hála and Navratil
• ISBN -807302053-X, Konvoj, 2003

Description: Good basic textbook on the subject, ideal for undergrads.