CHEM 1210 Lecture Notes - Lecture 2: Dmitri Mendeleev, Unified Atomic Mass Unit, Weighted Arithmetic Mean
Document Summary
Atomic weight: the weighted average of the masses (in amu) of the naturally occurring isotopes of an element (the number at the bottom of a square on the periodic table. Ex: 75. 77 of chlorine has an atomic mass of 34. 97amu and 24. 23% has an atomic mass of 36. 97amu. Chlorine is 75. 77% chlorine-35 and 24. 23% chlorine-37. [(75. 77/100) x 34. 97 amu] + [(24. 23/100) +36. 97 amu] : periodic table. Arranged known elements in order of increasing atomic weight beginning with hydrogen. Observed that when arranged in this manner, certain sets of properties recur periodically. Then arranged elements with recurring sets of properties in the same groups (columns) Li, na, and k, for example, fall in the same column and start new periods (horizontal rows) Are solids at room temperature (except for hg, which is a liquid), shiny, conduct electricity, and are ductile and malleable. Form alloys (solutions of one metal dissolved in another) Brass, for example, is an alloy of copper and zinc.
