Chemistry's Biggest Loser: Official Atomic Weights Change For 19 Elements | Popular Sci... - 0 views
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Improved measurements of different elements and their isotopes have changed the official atomic weights of 19 elements
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The changes are relatively small, and they're part of a regular effort to update atomic weights
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Every atom of an element
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silver as an example
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has the same number of protons
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Silver has 47
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not every atom of an element necessarily has the same number of neutrons
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different versions of an element's atoms are called isotopes
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Silver occurs as silver-109 and silver-107
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Chemists calculate the atomic weight of an element that you see on the periodic table from the masses of its isotopes, giving more common isotopes more weight than less common isotopes
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doesn't necessarily mean every sample of silver on Earth has an atomic weight of exactly
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samples of elements vary from place to place
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erences play an important role in many sciences
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They help chemists trace the origin of different materials
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and date archaeological findings
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The latest atomic weights measurements differ too little from their predecessors to really change science
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do it?"
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If it's just small changes, why
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should give the best numbers there are
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some new idea will come up that needs more accurate data
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Molybdenum, Losing 0.0122
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Atomic weights are relative, so they don't have units
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Thorium, Losing 0.000322
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Yttrium and Niobium, Tied, Losing 0.00001
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Selenium, Gaining 0.0088
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Cadmium, Gaining 0.0026
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Holmium, Thulium and Praseodymium, All Tied, Gaining 0.00001
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The changes in weights mostly come from continuing improvements in atomic mass measurements
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advances in the technology behind mass spectrometers
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not all about measuring more accurately
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thorium, the IUPAC decided to recognize an isotope, thorium-230, that it previously thought was too rare to include in atomic weight calculations
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The last time international chemistry
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really altered the periodic table was in 2009, when IUPAC decided to list the atomic weights of some elements as ranges, instead of single numbers