Nuclear Chemistry

Radioactive Decay Radiation is the release of subatomic particles and energy from the nuclei of unstable atoms. Atomic nuclei with even numbers of protons and neutrons tend to be more stable than those with odd numbers.

Nuclear Reactor

In a nuclear reactor, however, the neutrons are slowed and absorbed by control rods to control the reaction rate at a low level for a long time. TURKEY POINT

Band of Nuclear Stability

Alpha Decay The type of radiation known as alpha decay produces alpha particles. The emission of an alpha particle decreases the mass number by 4 and the atomic number by 2.

Beta Decay Beta particles (b) are high speed electrons generated from the decaying nucleus of an atom. Beta particles have little mass and a charge of -1. Beta decay is the "transformation" of a neutron into a proton, with the emission of an electron for charge conservation, and an antineutrino for energy and momentum conservation. The emission of a beta particle, b, from a neutron increases the atomic number by 1, but does not affect the overall mass. n  p + e - + ve, where ve is a neutrino

Gamma Decay Gamma rays (c) are high-energy photons or packages of electromagnetic energy. Gamma radiation only releases energy and does not affect the mass or atomic number of the atom.

Electron Capture The opposite of Beta decay, decreases the atomic number by 1, but does not affect the mass number. p + e-  n + ve.

Decay Series Decay occurs to return the nucleus to the band of stability.

Penetration of Radioactive Energy

Half-Life Half life is used to describe how long radioactive substances remain in the environment. Half-life is the time it takes one half of the radioactive atoms (nuclides) to decay to stable isotopes.

Half-life Simulation Remember: (1/2)2 = (1/2)(1/2) = ¼ This represents two half-lives. Note: half-life is an average. (1/2)3 = (1/2)(1/2)(1/2) = 1/8 This represents 3 half-lives, Etc.

Half – life Graphs

Half-Life Involves Calculus, but there is a simple way to solve these problems! The key question is always “how many halves?” So, let’s try a few (it’s the only way to get it!): What is the half-life of a 100.0 g sample of nitrogen-16 that decays to 12.5 g of nitrogen-16 in 21.6 s? 2. If the half-life of iodine-131 is 8.10 days, how long will it take a 50.00 g sample to decay to 6.25 g? 3. Potassium-42 has a half-life of 12.4 hours. How much of an 848 g sample of potassium-42 will be left after 62.0 hours?

Half-Life and Fossils

Fission The nuclei of very large atoms have the potential to split or fission into smaller nuclei. During this process, a small quantity of mass will be lost and converted into energy, as predicted by Einstein’s equation E=mc2. The energy is released in the form of heat and light.

In a nuclear reactor or in an atomic bomb, these neutrons are the means to carry out a chain reaction.

Chain Reaction In an atomic bomb, the neutrons are encouraged to split more and more atoms at a faster and faster rate. In a nuclear reactor, however, the neutrons are slowed and absorbed to control the reaction rate at a low level for a long time.

The Only Time in History the Atomic Bomb was Used in War  Nagasaki Hiroshima Hiroshima Nagasaki

Modern Nagasaki

Modern Hiroshima

Fusion Nuclear fusion is another way atoms can interact and release nuclear energy. In this process, the nuclei of small atoms combine with each other to produce larger, heavier atoms. The most common example is stellar fusion, where stars fuse hydrogen atoms to produce helium atoms. During this process, a tremendous amount of energy is released and a small amount of matter disappears. The mass that disappears, the mass defect, is converted into energy in the form of light and heat.

The End