Energy Unit Radioactivity

REVIEW: Nucleus Very Small Very Large Density Large amounts of Energy The typical nucleus is about 10-13 cm. .0000000000010 Very Large Density The typical density is about 1.6 x 1014 g/cm3. 160,000,000,000,000 Large amounts of Energy The typical nuclear process produces millions of times more energy than those associated with normal chemical processes.

REVIEW Nuclear Symbols Mass number (p+ + no) Element symbol Atomic number (number of p+)

Radioactive Decay Radioactivity Nuclear Equation when a nucleus spontaneously decomposes, forming a different nucleus and producing one or more particles. Nuclear Equation Both the atomic number and the mass number must be conserved. That is the sums of both on each side must be equal.

When an unstable nucleus decays, there are three particles it may produce: an alpha particle (symbol ) a beta particle (symbol ) a gamma ray (symbol )

Types of Radioactive Decay Alpha-particle Production Alpha particle is a helium nucleus Atomic number of helium is 2; mass number is 4.

Alpha Radiation Limited to VERY large nuclei.

Types of Radioactive Decay Beta-particle production A beta-particle is an electron. The net effect of beta-particle production is to change a neutron to a proton. No change in mass number, but an increase in one in atomic number.

Beta Radiation Converts a neutron into a proton.

Types of Radioactive Decay Gamma Ray A high-energy photon of light. A nuclide in an excited nuclear energy state can release excess energy by producing gamma rays. Gamma rays are photons of light so they have zero charge and zero mass number.

Types of Radioactive Decay Positron Production The positron is a particle with the same mass as an electron but opposite charge. Does not occur often enough to make it practical to change mercury to gold. Results in no change of mass, but a decrease of 1 in atomic number.

Types of Radioactive Decay Electron Capture A process in which one of the inner-orbital electrons is captured by the nucleus. Atomic number decreases by one. Mass remains the same.

Types of Radiation

Alpha particles are easy to stop, gamma rays are hard to stop.

Decay Series Often radioactive nucleus cannot achieve stable state through a single decay process. A decay series will occur until a stable nuclide is formed.

Nuclear Fission The process of splitting an atom. http://www.teachersdomain.org/asset/phy03_vid_fission/ The process of splitting an atom. Releases an enormous amount of energy. 1 mol of uranium-238 can produce about 26 million times as much energy as 1 mol of methane.

Nuclear Fusion The process of combining two light nuclei. Produces more energy than fission. http://www.teachersdomain.org/asset/phy03_vid_fusiontest/