Oxidation Numbers

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Oxidation Numbers
0
1
3-
2-
2
3
4
1-
Variable Oxidation States
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Naming Binary Compounds(Ionic Compounds)

• To name compounds of elements having two or more
  oxidation numbers you must first figure out the
  oxidation numbers of the elements.
• Example What is the name of CrO?
• Cr is a transition metal so its oxidation number
  will vary.
• O oxidation number is 2-
• In order for this to be a stable compound Cr
  oxidation number must be 2
• Because Cr is a transition metal you must include
  the roman numerals in the name.
• What is the name of the compound?
• Chromium (II) oxide
• The last element always ends in ide

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Naming Binary CompoundsIonic Naming

• When naming, always name the cation (positive
  ion) first with its full name. Then name the
  anion (negative ion) second. Replace the end of
  the anion with the ending ide
• Example NaCl the cation is Na the anion is Cl
• Na sodium Cl chlorine
• Put the two together and change the ending of
  chlorine to ide
• Sodium Chloride!!

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Naming Binary Compounds

• Try some examples
• NaF
• CaCl2
• KBr
• CaO
• CuI
• Mg3N2

Sodium Floride Calcium Chloride Potassium
Bromide Calcium Oxide Copper Iodide or Cupric
Iodide Magnesium Nitride
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Naming Covalent Compounds(molecular naming)

• To name a compound covalently you must tell how
  many atoms of each element are in the compound.
• Ex BF3 Boron Triflouride
• There is 1 boron and 3 flourine

Mono 1 Bi or di 2 Tri 3 Tetra 4 Penta
5 Hexa 6 Hepta 7 Octa 8 Nona 9 Deca 10
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Naming Covalent Compounds

• Try these
• N2O4
• As2O5
• SiI4
• P4S3

Dinitrogen tetroxide Diarsenic pentoxide Silicon
tetriodide Tetraphosphorus trisulfide
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Compounds with Polyatomic Ions

• What is a polyatomic ion??
• The prefix poly means many, so polyatomic
  means having many atoms.
• A polyatomic ion can be either positively charged
  or negatively charged group of atoms. The entire
  compound can have 3 or more elements.

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Names with Polyatomic Ions

• To name a compound that has one of the polyatomic
  ions you must
• Write the name of the POSITIVE element first.
• Write the name of the NEGATIVE element second.
• When more than one molecule of the polyatomic ion
  is in the formula, write parentheses around the
  polyatomic ion.
• Ex K2SO4 what is the name of the positive ion?
  What is the name of the negative ion?
• The positive ion is Potassium, the negative ion
  is Sulfate
• The name of the compound is Potassium sulfate
• K2 is Potassium SO4 is the polyatomic ion
  Sulfate

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Formulas with Polyatomics

• In an example of a polyatomic compound where
  there are more than one polyatomic atoms in the
  compound YOU MUST PUT PARENTHESES AROUND THE
  COMPOUND with the number of atoms outside the
  parentheses.
• Mg(NO3)2 What is the polyatomic ion? How many
  of them are there?
• The polyatomic atoms is NO3. There are 2 of
  these molecules.

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Writing a Chemical FormulaCriss Cross Method
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The same method applies to formulas with simple
elements!