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Do Now

Do Now. Do Now: Write the electron dot diagram (Lewis dot diagram) for MgO. Chemical Formulas. How to Interpret Them. Interpreting Chemical Formulas. Consider the formula below: The formula has subscripts, Each of these has a function. parentheses. dot. coefficient.

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Do Now

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  1. Do Now • Do Now: • Write the electron dot diagram (Lewis dot diagram) for MgO.

  2. Chemical Formulas How to Interpret Them

  3. Interpreting Chemical Formulas • Consider the formula below: • The formula has subscripts, • Each of these has a function. parentheses dot coefficient Fe2(SO4)3●9H2O subscripts parentheses, a coefficient, and a dot. WRITE DOWN

  4. Subscripts • A subscript is a small number written to the lower right of the symbol. • It shows the number of atoms or polyatomic ions in a formula. • A subscript 1 (one) is never written. It is understood. • How many iron atoms are in the formula above? Fe2(SO4)3●9H2O subscripts WRITE DOWN WRITE DOWN 2

  5. Parentheses • Parentheses are written around polyatomic ions when there are more than one of the ion. • Polyatomic ions are charged groups of atoms. • Some polyatomic ions are found on the Reference Tables. • How many sulfate ions are in the formula above? How many sulfur atoms? How many oxygen atoms are in the sulfates? parentheses Fe2(SO4)3●9H2O WRITE DOWN WRITE DOWN 3 3 12

  6. Coefficients • Coefficients are large numbers written to the left of the formula. • They multiply every atom in the following molecule. • The formula above has 18 H atoms. coefficient Fe2(SO4)3●9H2O WRITE DOWN WRITE DOWN

  7. The Dot • The dot is used as a separator between two substances in a formula. • Mathematically, the dot acts like a plus sign. • A plus sign has another function in chemistry, so it cannot be used in a formula. • How many oxygen are in Fe2(SO4)3·9H2O? dot Fe2(SO4)3●9H2O WRITE DOWN WRITE DOWN 21

  8. Counting Atoms • How many atoms of each element are in the formula below and what is the total number of atoms: 5Fe2(SO4)3●9H2O

  9. Regents Questions

  10. Regents Questions

  11. Regents Questions

  12. Regents Questions

  13. Check Your Answers

  14. Check Your Answers

  15. Interpreting Chemical Formulas Quiz • For each of the following formulas, write the name of each element and the number of atoms of that element in the formula: 3Al(OH)3 5FE2(SO4)3 • BONUS • Write the names of the polyatomic ion present in each formula.

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