Chapter 18
Mass # Symbol Element Name or symbol – Mass # Parts of a Reaction Reactants Products
Alpha emission or decay ( ) –helium atom 4 2 He U 4 2 He Th Beta emission or decay ( )– 0 -1 e in the products Th Pa e Gamma emission or decay ( ) U 4 2 He Th
Positron emission or decay e Na 0 +1 e Ne Electron capture – beta particle in the reactants Hg e Au Neutron emission or decay– 1 0 n Po 1 0 n Po Proton – 1 1 H or 1 1 p
Mass # and the atomic # totals must be the same for reactants and the products. K Cl + ___ Pb 0 -1 e + ___ Pu + ___ 4 2 He U
Alpha decay of Cu-68 Gamma emission of Thorium-235 Positron emission of P-18 Astatine-210 releasing 3 neutrons Electron capture of Ti-45
Radioactive isotopes or nuclides all decay because they are unstable, some just breakdown much faster than others Half-life – amount of time for half of the original sample to decay For two samples of the same isotope, regardless of the sample size, after one half- life, only half of the original amount of sample remains.
IsotopesHalf-Live Carbon – years Sodium – 2415 hours Bismuth – seconds Polonium – seconds Thorium – years Thorium – days Uranium – x 10 8 years Uranium – x 10 9 years
Barium – 139 has a half-life of 86 minutes. If you originally have a 10 gram sample of Barium-139, how much will be left after 258 minutes?
How many days will it take 50 grams of Radon – 222 (half-life of 3.82 days) to decay to grams?
If a sample of Cesium-135 decays from 10 grams to 2.5 grams over a period of 84 days, what is the half-life of Cesium-135?
Fusion – combining two smaller nuclei into one heavier, more stable nucleus. 3 2 He H 4 2 He e Fission – splitting a large unstable nucleus into two nuclei with smaller mass numbers Po Te Ge