Ch. 28 – Nuclear Chemistry Nuclear Radiation, Nuclear Transformations, Fission & Fusion of Atomic Nuclei

Nuclear Radiation Nuclear Rxn = radioisotopes gain stability by undergoing changes in the nuclei accompanied by the emission of large amounts of energy Radiation = penetrating rays & particles emitted by a radioactive source; Marie & Pierre Curie isolated several radioactive elements & with Becquerrel won the Nobel Prize in 1903 cleat

Check out Table 28.1 There are three main types of radiation: alpha particles: These are small bits of nucleus. They are made of 2 protons and 2 neutrons. They have a positive electric charge. beta particles: These are the loose electrons left over when the atoms break apart. They have a negative electric charge. gamma rays: These are actually electromagnetic energy waves. They do not have an electric charge. Check out Table 28.1

Alpha Radiation The reason alpha decay occurs is because the nucleus has too many protons which cause excessive repulsion. In an attempt to reduce the repulsion, a Helium nucleus is emitted. That is, an alpha particle (Helium nucleus) will tunnel out of the nucleus. Here is an example of alpha emission with americium-241:

Alpha cont.. The Equation is balanced..

Beta Radiation Beta decay occurs when the neutron to proton ratio is too great in the nucleus and causes instability. In basic beta decay, a neutron is turned into a proton and an electron. The electron is then emitted. Here's beta decay with hydrogen-3:

Gamma Radiation Gamma decay occurs because the nucleus is at too high an energy. The nucleus falls down to a lower energy state and, in the process, emits a high energy photon known as a gamma particle. Here's a diagram of gamma decay with helium-3:

Penetrating Power

Nuclear Transformations

Calculating Half-life If a substance has a half life of 24 min. and you have 2.00 g, then how long is 3 half lives and how much would be left? 3 x 24 = 72 min 2.00g x .5 x .5 x .5 = .250 g

Transmutation Rxn The conversion of an atom of one element to an atom of another element = transmutation Occurs in the upper atmosphere with the production of carbon-14. Transuranium elements – after 92 on periodic table; all undergo transmutations.

Nuclear Fission The splitting of a nucleus into smaller fragments Releases enormous amounts of energy Occurs in nuclear reactors

Nuclear Fusion Nuclei combine to form a nucleus with greater mass Requires a high temp to start the rxn Occurs in stars

Detecting Radiation Geiger counter Film Badge (photographic plate) Scintillation counter electroscope