Splitting atoms Nuclear chemistry

Another area of general chemistry with which you should be familiar is the study of radioactivity, or nuclear chemistry. Specifically, nuclear chemistry deals with the properties of the nucleus of the atoms that s why it is called nuclear chemistry. 

As you progress through the periodic table each successive atom has one more proton and neutron compared with the previous atom. The protons are useful for attracting electrons, and the neutrons are useful for stabilizing the nucleus. When there is an imbalance between the two nuclear particles (proton and neutron), the nucleus becomes unstable, and these types of atoms are called isotopes. If they are radioactive, they are called radioisotopes, and they can be useful, for example, in medical applications. 

Although you may immediately think about nuclear reactors for energy, or nuclear bombs and their incredible devastation, concepts in nuclear chemistry are applied for many other, less dramatic purposes, one such example is carbon dating of ancient materials (see Chapter 4). 

The nuclear processes can affect the properties of the atoms, and this can have an effect on the properties of materials that are made with those atoms. For example, there is often a lot of heat generated by radioactive atoms, and this heat can affect material properties. Did you know that much of the potassium in our body is in the form of a radioactive isotope This accounts for some of the heating within our own bodies (see Chapter 11). 

In Chapter 5, we explain the basics of acids and bases, including how the pH scale was developed to quantify the strength of different acids and bases. It s a simple system that ranges in value from pH 1 to pH 14. 

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J Ju elements in the periodic table exist in unstable versions called radioisotopes (see Chapter 3 for details). These radioisotopes decay into other (usually more stable) elements in a process called radioactive decay. Because the stability of these radioisotopes depends on the composition of their nuclei, radioactivity is considered a form of nuclear chemistry. Unsurprisingly, nuclear chemistry deals with nuclei and nuclear processes. Nuclear fusion, which fuels the sun, and nuclear fission, which fuels a nuclear bomb, are examples of nuclear chemistry because they deal with the joining or splitting of atomic nuclei. In this chapter, you find out about nuclear decay, rates of decay called half-lives, and the processes of fusion and fission. 

Rutherford s work has made him known as the father of nuclear physics with his research on radioactivity (alpha and beta particles and protons, which he named), and he was the first to describe the concepts of half-life and decay constant. He showed that elements such as uranium transmute (become different elements) through radioactive decay, and he was the first to observe nuclear reactions (split the atom in 1917). In 1908 he received the Nobel Prize in chemistry for his investigations into the disintegration of the elements, and the chemistry of radioactive substances. He was president of the Royal Society (1926-30) and of the Institute of Physics (1931-33) and was decorated with the Order of Merit (1925). He became Lord Rutherford in 1931. 

Hahn, Otto. (1879-1968). A German physical chemist who won the Nobel Prize for chemistry in 1944 for atom splitting and the principle of the chain reaction. Well-known for work on nuclear fission he discovered protactinium and transuranium elements with atomic numbers 94,95, and 96. After receiving his doctorate at the University of Munich, he worked in Canada before returning to Europe. 

In practice, most of the collisions of interest in cold molecule studies involve collision partners with internal structure. Many of the atoms and molecules of interest have unpaired spins, and molecules have vibrational and rotational levels. Even nuclear hyperfme splittings, which are small enough to be neglected in many areas of chemistry, are large enough to be important in cold molecule studies. It is thus crucial to be able to handle collisions between atoms and molecules with internal structure. Although methods based on classical trajectories have had considerable success for inelastic and reactive collisions at room temperature or higher [3], for cold atoms and molecules it is almost always necessary to treat the collisions quantum-mechanically. 

A typical molecule in synthetic organic chemistry today may have more than 20 distinct carbon and proton signals, and the chemical shifts alone are not sufficient to determine the structure of such a complicated system. But after one has looked at the chemical shifts to get a rough idea of what environments exist in the molecule, there is often much more information available from the interactions between neighboring nuclear spins. Protons commonly have several neighbors with non-zero nuclear spin (such as other H atoms, N, C), so we will examine splittings in the proton NMR spectrum. 

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