补全短文（第46～50题，每题2分，共10分）
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Reinventing the Table
An earth scientist has rejigged the periodic table to make chemistry simpler to teach to students. 46 But Bruce Railsback from the University of Georgia says he is the first to create a table that breaks with tradition and shows the ions of each element rather than just the elements themselves.
"I got tired of breaking my arms trying to explain the periodic table to earth students." he says, crisscrossing his hands in the air and pointing to different bits of a traditional table. 47 But he has added contour lines to charge density, helping to explain which ions react with which. "Geochemists just want an intuitive sense of what's going on with the elements," says Albert Galy from the University of Cambridge 48.
49 He explains that sulphur, for example, shows up in three different spots one-for sulphide, which is found in minerals, one for sulphite, and one for sulphate, which is found in sea slat, for instance. He has also included symbols to show which ions are nutrients, and which are common in soil or water. 50
A There have been many attempts to redesign the periodic table since Dmitri Mendeleev drew it up in l871.
B Railsback has still ordered the elements according to the number of protons they have.
C "I imagine this would be good for undergraduates."
D Railsbaek has listed some elements more than once.
E And the size of element's symbol reflects how much of it is found in the Earth's crust.
F The traditional periodic table was well drawn.
