General Science

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General Science

• 9.2 Chemical Formulas

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Warm Up 01.25.07

• How many hydrogens and oxygens are in H2O? How
  do you know?

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Chemical Formula

• A shorthand way to represent the composition of a
  pure substance
• It tells us the number and type of atom presented
• The symbols represent the type of atom
• The subscripts (numbers below the line) indicate
  the number of atoms

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Practice

• How many atoms of each element are in the
  following formulas?
• CCl4
• N2O2
• NaSO4
• (NH4)2CO3

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Unique Molecules

• Molecules are unique based on the number and
  types of atoms
• HOWEVER, sometimes the formula can be the same,
  but the structures are different
• So we need different types of formulas to help us
  figure out which molecule it is

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Molecular Formulas

• These are formulas that show us how many and type
  of atoms are in a single molecule or formula unit
  of a compound
• What is the difference between a molecule and a
  formula unit?

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Structural Formulas

• These formulas show us the bonds between the
  atoms in a molecule or formula unit.
• This one would allow us to compare two molecular
  formulas to determine if they are the same
  compound.

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Empirical Formula

• These formulas show only the relative proportion
  of atoms in a molecule
• For example, the molecular formula for glucose is
  C6H12O6, but we could simplify the formula to
  CH2O