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Published byMelissa Shaw Modified over 9 years ago
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Chemical Symbols & Formulas their development and use
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Greek Symbols gold mercury copper silver iron tin lead
iron tin lead
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Alchemical Symbols Each alchemist had his/her own symbols.
Symbols were designed for handwritten (not printed) pages. Alchemists were more concerned with secrecy than communication.
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John Dalton’s System 50. Sulfuric acid 10. Calcium nitrate Dalton used differently shaped circles for each element. He then showed compounds as combinations of these symbols, based on his atomic theories. Symbols = Compounds =
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Jons Jacob Berzelius c. 1815 He suggested using LETTERS of NAMES as symbols, with SUBSCRIPTS. We still do. This made type-setting chemical formulas cheaper and easier. These symbols are UNIVERSAL, and independent of the language used for the name. A Swedish chemist, most of Berzelius’ symbols are based on Latin names of elements.
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Counting Atoms H2O = 2 hydrogen, 1 oxygen
SUBSCRIPTS describe elements they follow. Cu(NO3)2 = 1 copper, 1x2=2 nitrogen,2x3= 6 oxygen PARENTHESES work as multipliers, just like math. DOTS are the only symbol that’s different in chemistry and math. They denote a PHYSICAL connection rather than a chemical bond. CuSO4. 5H2O = 1 copper, 1 sulfur, 4+5 = 9 O, 5x2=10 H “DOTS” act like “+” signs, unlike in math. COEFFICIENTS act as multipliers until the next “dot”.
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Problems to Try Count atoms per element in these compounds.
Lodestone Fe3O4 Methanol CH3OH Plexiglass CH2CCH3COOCH Trinitrotoluene C6H2CH3(NO2)3 Acetone C(CH3)2O Prussian Blue Fe4[Fe(CN)6]3 Yellow ochre Fe2O3.2H2O Lead white 2PbCO3.Pb(OH)2 Lapus lazuli 3Na2O.3Al2O3.6SIO2.2Na2S Paris green Cu(C2H3O2)2.3Cu(ASO2)3 What do think is meant by this formula for opal: SiO2.nH2O? Note: Formulas like the ones for Plexiglass and methanol are “hiding” extra information on how the atoms are connected to one another - that’s why all the atoms of the same element are not grouped together. This is also the principle behind using parentheses.
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Answers 3 iron, 4 oxygen 1 carbon, 4 hydrogen, 3 oxygen
7 carbon, 5 hydrogen, 3 nitrogen, 6 oxygen 3 carbon, 6 hydrogen, 1 oxygen 7 iron, 18 carbon, 18 nitrogen 2 iron, 5 oxygen, 4 hydrogen 3 lead, 2 carbon, 8 oxygen, 2 hydrogen 10 sodium, 24 oxygen, 6 aluminum, 6 silicon, 2 sulfur 5 copper, 4 carbon, 6 hydogen, 22 oxygen, 9 arsenic He “n” means “a variable amount”
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