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Chemical Formulas

Chemical Formulas. 10/16/12 Class Notes. Pg3……..Chemical Formulas. 1 st Rule of Symbols: Chemical symbols consist of either a capital letter or a capital letter and lower case letter. This means that at least one atom of this element is present in the compound. Carbon monoxide. CO.

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Chemical Formulas

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  1. Chemical Formulas 10/16/12 Class Notes

  2. Pg3……..Chemical Formulas 1st Rule of Symbols: Chemical symbols consist of either a capital letter or a capital letter and lower case letter. This means that at least one atom of this element is present in the compound. Carbon monoxide CO 1 carbon 1 oxygen = 2 atoms Table salt NaCl 1 sodium 1 chlorine = 2 atoms 2 atoms bonded together 2 atoms bonded together

  3. Pg3……..Chemical Formulas 2nd Rule of Subscripts: The subscript goes with the element it directly follows and indicates how many atoms of that element are present. Carbon dioxide CO2 The “subscript” number comes after the element it describes 1 carbon 2 oxygen = 3 atoms There are 2 oxygen atoms bonded to the 1 carbon atom Water H2O 2 hydrogen 1 oxygen = 3 atoms When no number appears after an element, the compound is assumed to contain only 1 of that element The “subscript” 2 means there are 2 hydrogen atoms bonded to the 1 oxygen

  4. OH Ba OH Pg3……..Chemical Formulas 3rd Rule of Parenthesis: The elements in the () go with the subscript that follows it. Numbers inside the () are multiplied by the subscript number outside the (). Ba(OH)2 The “subscript” after a ( ) is the number of groups in the compound Elements inside the parenthesis stay grouped together 1 Barium 2 Oxygen 2 Hydrogen =5 atoms in compound

  5. Pg3……..Chemical Formulas (NH4)3PO4 Subscript 4 describes the number of oxygens in compound There are 3 groups of NH4 in compound NH4 stays grouped together in compound Subscript number outside of parenthesis is multiplied through when counting atoms. N : 1 x 3 = 3 atoms H : 4 x 3 = 12 atoms P : 1 atom O : 4 atoms = 20 atoms in compound

  6. Pg3……..Chemical Formulas OH OH OH Ba Ba Ba OH OH OH 4th Rule of Coefficients: The coefficient on a chemical compound tells how many molecules of that compound are present. The coefficient applies to every element in the compound and is multiplied with any subscripts present on an element. 3Ba(OH)2 coefficient 3 x 1 = 3 Bariums 3 x 2 = 6 Oxygens 3 x 2 = 6 Hydrogens =15 atoms total present

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