Chapter 21: Nuclear Chemistry Chemistry 1062: Principles of Chemistry II Andy Aspaas, Instructor

Nuclear chemistry Chemical reactions where the nuclei change Independent of chemical surroundings (i.e. it doesn’t matter what compounds the nuclei are part of) Radioactive decay: unstable nuclei spontaneously disintegrate and give off radiation Nuclear bombardment reactions: one nucleus is physically struck by another nucleus to cause a nuclear reaction

Nuclear equations Nuclei only! Nuclide symbols used to show: –Mass number, A –Atomic number, Z For particles with no protons, the atomic number represents the charge –Ex. electron: Total mass numbers and atomic numbers must be equal on both sides of reaction

Radioactivity Alpha emission: ejection of a helium-4 nucleus –Occurs in nuclei where Z > 83 (transuranium) –Ex. Beta emission: ejection of a high-speed electron –Occurs when N/Z is too large (N = # neutrons) –Ex.

Radioactivity Positron emission: ejection of a positron –Positron: positively charged particle with same mass as an electron –Occurs when N/Z is too small –Ex. Electron capture: adding an electron to the nucleus –Competes with positron emission when N/Z is too small –Ex.

Radiation Gamma emission: emission of a gamma photon from an excited state nucleus –Metastable nucleus: excited nucleus a lifetime of at least one nanosecond –Ex. Spontaneous fission: when a nucleus Z > 89 spontaneously breaks apart into other nuclei –Ex.

Predict the decay Predict the form of radioactive decay the following nuclei will have, and if possible, write a nuclear equation

Nuclear bombardment reactions Nuclei such as uranium-235 can be caused to split into several other nuclei if bombarded by a neutron –Fission produces more neutrons, which can go on to cause other uranium nuclei to split The result is a chain reaction which releases the energy of neutron bombs and nuclear fission reactors

Nuclear fission reactor Pressurized light water reactor Most common design in US Prairie Island, MN

Prairie Island Nuclear Generating Plant, Red Wing, MN