NOTES: 6'16'2 Chemical Compounds and Formulas

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NOTES 6.1-6.2 Chemical Compounds and Formulas
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ELEMENTS

• ? the building blocks of matter
• ? about 100 elements, but millions of compounds
  made from their atoms
• ? there must be a common method for naming
  chemical compounds

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MONATOMIC ELEMENTS

• ? consists of a single atom
• ? EX the noble gases (He, Ne, Ar)

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MOLECULE

• ? made up of 2 or more atoms that act as a unit
• ? the smallest, electrically neutral unit of a
  substance that still shows the properties of that
  substance
• ? EX oxygen gas oxygen molecules

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MOLECULAR COMPOUNDS

• ? compounds composed of MOLECULES
• ? composed of atoms of 2 or more nonmetals
• ? EXAMPLES
• ? carbon monoxide CO
• ? oxygen O2
• ? water H2O
• ? ammonia NH3

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IONS

• ? atoms OR groups of atoms that have a positive
  or negative charge
• ? form when an atom or group of atoms gains or
  loses electrons
• ? CATIONS positive ions
• ? ANIONS negative ions

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EXAMPLE

• ? lithium atom 3 pro () 3 elec (-)
• ? lithim ION
• ? RESULT

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EXAMPLE

• ? lithium atom 3 pro () 3 elec (-)
• ? lithim ION 3 pro () 2 elec (-)
• ? RESULT

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EXAMPLE

• ? lithium atom 3 pro () 3 elec (-)
• ? lithim ION 3 pro () 2 elec (-)
• ? RESULT Li LITHIUM ION

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EXAMPLE

• ? fluorine atom 9 pro () 9 elec (-)
• ? fluoride ION
• ? RESULT

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EXAMPLE

• ? fluorine atom 9 pro () 9 elec (-)
• ? fluoride ION 9 pro () 10 elec (-)
• ? RESULT

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EXAMPLE

• ? fluorine atom 9 pro () 9 elec (-)
• ? fluoride ION 9 pro () 10 elec (-)
• ? RESULT Cl- CHLORIDE ION

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IONS, continued

• ? the METALS tend to form CATIONS
• ? calcium forms Ca2 (calcium ion)
• ? aluminum forms Al3 (aluminum ion)
• ? the NONMETALS tend to form ANIONS
• ? bromine forms Br - (bromide ion)
• ? sulfur forms S2- (sulfide ion)

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IONIC COMPOUNDS

• ? compounds composed of pos. and neg. ions
• ? usually composed of a METAL CATION and NONMETAL
  ANION
• ? EXAMPLES
• ? sodium chloride NaCl
• ? strontium oxide SrS
• ? aluminum sulfide Al2S3

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Chemical Formula

• ? Represents the kinds and numbers of elements in
  the smallest unit of a substance (molecule or
  formula unit)
• ? If the molecules of an ELEMENT have more than
  one atom, you use a subscript
• ? EXAMPLES O2, Cl2, Br2

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Molecular Formula

• ? Represents the kinds and numbers of elements in
  a molecule of a molecular compound
• ? EXAMPLES each molecule contains
• ? CO
• ? PCl5
• ? H2O

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Molecular Formula

• ? Represents the kinds and numbers of elements in
  a molecule of a molecular compound
• ? EXAMPLES each molecule contains
• ? CO 1 C atom 1 O atom
• ? PCl5
• ? H2O

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Molecular Formula

• ? Represents the kinds and numbers of elements in
  a molecule of a molecular compound
• ? EXAMPLES each molecule contains
• ? CO 1 C atom 1 O atom
• ? PCl5 1 P atom 5 Cl atoms
• ? H2O

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Molecular Formula

• ? Represents the kinds and numbers of elements in
  a molecule of a molecular compound
• ? EXAMPLES each molecule contains
• ? CO 1 C atom 1 O atom
• ? PCl5 1 P atom 5 Cl atoms
• ? H2O 2 H atoms 1 O atom

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Formula Units

• ? Represents the lowest whole number ratio of
  ions in an ionic compound
• (in ionic compounds, there are no molecules,
  just a continuous array of ions in a fixed ratio)
• ? EXAMPLES each formula unit contains
• ? CaF2
• ? NaF
• ? Fe(NO3)2

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Formula Units

• ? Represents the lowest whole number ratio of
  ions in an ionic compound
• (in ionic compounds, there are no molecules,
  just a continuous array of ions in a fixed ratio)
• ? EXAMPLES each formula unit contains
• ? CaF2 1 Ca2 ion 2 F- ions
• ? NaF
• ? Fe(NO3)2

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Formula Units

• ? Represents the lowest whole number ratio of
  ions in an ionic compound
• (in ionic compounds, there are no molecules,
  just a continuous array of ions in a fixed ratio)
• ? EXAMPLES each formula unit contains
• ? CaF2 1 Ca2 ion 2 F- ions
• ? NaF 1 Na ion 1 F- ion
• ? Fe(NO3)2

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Formula Units

• ? Represents the lowest whole number ratio of
  ions in an ionic compound
• (in ionic compounds, there are no molecules,
  just a continuous array of ions in a fixed ratio)
• ? EXAMPLES each formula unit contains
• ? CaF2 1 Ca2 ion 2 F- ions
• ? NaF 1 Na ion 1 F- ion
• ? Fe(NO3)2 1 Fe2 ion 2 NO3- ions
• (1 Fe, 2 N, 6 O)