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Bellringer

Bellringer. 1. What is the chemical formula for water? 2. How many hydrogen atoms are in a water molecule? 3. How many oxygen atoms are in a water molecule?. COUNTING ATOMS. Chemical Formulas. Tell what elements make up the compound and the number of atoms of each element.

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Bellringer

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  1. Bellringer 1. What is the chemical formula for water? 2. How many hydrogen atoms are in a water molecule? 3. How many oxygen atoms are in a water molecule?

  2. COUNTING ATOMS

  3. Chemical Formulas • Tell what elements make up the compound and the number of atoms of each element.

  4. RULES FOR COUNTING ATOMS • SUBSCRIPTS only refer to the atom that they are BEHIND. For example… H2S There are TWO atoms of HYDROGEN and only ONE atom of SULFUR.

  5. COEFFICIENTS • COEFFICIENTS apply to the entire compound. You MULTIPLY the coefficients and SUBSCRIPTS. 2H2S ATOMS OF HYDROGEN: ATOMS OF SULFUR: 4 2 IF THERE ISN’T A SUBSCRIPT BEHIND AN ELEMENT, ASSUME THERE IS ONLY ONE ATOM OF THAT ELEMENT!

  6. Polyatomic ions • A group of atoms that act as a single atom. • Put in parentheses

  7. PARENTHESES 3. If elements or compounds are inside of PARENTHESES, then the SUBSCRIPT behind the parentheses applies to everything inside. Ba(OH)2 ATOMS OF BARIUM: ATOMS OF OXYGEN: ATOMS OF HYDROGEN: 1 2 2

  8. LET’S PRACTICE! MgCl2 Atoms of Magnesium: Atoms of Chlorine: 1 2 Al2S3 Atoms of Aluminum: Atoms of Sulfur: 2 3

  9. PRACTICE H2SO4 Atoms of Hydrogen: Atoms of Sulfur: Atoms of Oxygen: 2 1 4 CH3OH Atoms of Carbon: Atoms of Hydrogen: Atoms of Oxygen: 1 4 1

  10. THIS COULD BE A LITTLE TRICKY… Ca3(PO4)2 Atoms of Calcium: Atoms of Phosphorus: Atoms of Oxygen: 3 2 8 Al2(SO4)3 Atoms of Aluminum: Atoms of Sulfur: Atoms of Oxygen: 2 3 12

  11. What about this BAD BOY??? 2Ca3(PO4)2 Atoms of Calcium: Atoms of Phosphorus: Atoms of Oxygen: 6 4 16

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