Counting Atoms

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Counting Atoms

  1. 1. COUNTING ATOMS
  2. 2. RULES FOR COUNTING ATOMS1. SUBSCRIPTS only refer to the atom that they are BEHIND. For example… H2 S There are TWO atoms of HYDROGEN and only ONE atom of SULFUR.
  3. 3. COEFFICIENTS2. COEFFICIENTS apply to the entire compound. You MULTIPLY the coefficients and SUBSCRIPTS. 2 H2 S ATOMS OF HYDROGEN: 4 ATOMS OF SULFUR: 2 IF THERE ISN’T A SUBSCRIPT BEHIND AN ELEMENT, ASSUME THERE IS ONLY ONE ATOM OF THAT ELEMENT!
  4. 4. PARENTHESES3. If elements or compounds are inside of PARENTHESES, then the SUBSCRIPT behind the parentheses applies to everything inside. Ba(OH)2 ATOMS OF BARIUM: 1 ATOMS OF OXYGEN: 2 ATOMS OF HYDROGEN: 2
  5. 5. LET’S PRACTICE! MgCl2Atoms of Magnesium: 1Atoms of Chlorine: 2 Al2S3Atoms of Aluminum: 2Atoms of Sulfur: 3
  6. 6. PRACTICE H2SO4Atoms of Hydrogen: 2Atoms of Sulfur: 1Atoms of Oxygen: 4 CH3OHAtoms of Carbon: 1Atoms of Hydrogen: 4Atoms of Oxygen: 1
  7. 7. THIS COULD BE A LITTLE TRICKY… Ca3(PO4)2Atoms of Calcium: 3Atoms of Phosphorus: 2Atoms of Oxygen: 8 Al2(SO4)3Atoms of Aluminum: 2Atoms of Sulfur: 3Atoms of Oxygen: 12
  8. 8. What about this BAD BOY??? 2Ca3(PO4)2Atoms of Calcium: 6Atoms of Phosphorus: 4Atoms of Oxygen: 16

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