CHEM 1AA3 Lecture Notes - Structural Formula, Chemical Formula, Empirical Formula
12 Mar 2014
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Document Summary
Empirical formula: reduces to the most common denominator of molecule. For instance, empirical formula for benzene is ch, while molecular formula is c6h6. Molecular formula: actual numbers of each element are represented. Condensed formula: empirical formula in brackets, with common denominator on the outside. For instance, the condensed formula for benzene is (ch)6. Isotopes: elements which share the same # of protons, but differ in # of neutrons and therefore differ in mass #. A = mass number (neutrons +protons) z = atomic # (number of protons) Z identifies which element it is, a identifies the isotope. Isotopes have natural abundance, which means they are found in statistically uniform distributions around the world. Finding changes/trends in these distributions allow scientists to analyze changes in nature, i. e. calibrating rainfall vs. snowfall per era in glacial deposits. Measuring 18o/16o ratios in ice cores lets us measure" past world t (with data calibrated against the recent past) evidence for global warming.
