Chapter 17; Radioactivity and Nuclear Chemistry Radioactivity Until now we have been looking at the chemistry of atoms with stable nuclei. Most chemistry deals with gaining, losing and sharing electrons. Nuclear chemistry is a branch of chemistry which works with isotopes that have nuclei which are NOT stable. In nuclear chemistry one element often changes into another Radioactive Nuclei 1896 Henri Becquerel Photographic plate and rock containing uranium Marie and Pierre Curie Much early work with radioactivity Good short history in your text. Transmutation: Any change from one element into another Isotopes Atomic number: Number of protons Mass Number: Number of protons plus number of neutrons Nucleon: Either a proton OR a neutron When writing isotopes the mass number is always on top and the protons is always on the bottom. Isotopes Isotopes are not necessarily radioactive . They may be stable or unstable. Isotopes of Hydrogen 1H, 2H, 3H 1H & 2H, are stable 3H is unstable Isotopes of Carbon 11C, 12C, 13C, 14C 12C and 13C are stable 11C and 14C are unstable Nuclide: FOCUSES ON THE NUCLEUS More general term, refers to nuclei of same or different elements (as opposed to atoms of different types) Stable Isotopes vs. Radioactive All isotopes with 84 or more protons are unstable With low atomic weight elements, stable isotopes have about a 1:1 proton: neutron ratio With higher atomic weight elements the ratio is about 2 protons to 3 neutrons Different Decay Products Lead is often used Beta particles are negatively charges so they are pushed away from the negative electrode and toward the positive electrode. Alpha particles are positively charges so they are pushed away from the positive electrode and toward the negative electrode.
Type Symbol Mass Charge Description Alpha 4 2 α 4 2 Helium nuclei Beta 0 -1 β 0 -1 Electrons produces and ejected from nucleus Gamma 0 0 γ 0 0 Electromagnetic radiation Neutron 1 0 n 1 0 Neutrons Positron 0 +1 β 0 +1