Chemistry Lecture 3C

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Chemistry Lecture 3C

• Names and Formulas of Chemical Compounds
• (Inorganic)

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Formula to Name

• First, you must ask yourself if the given
  compound is inorganic.
• It is an inorganic compound if it does not
  contain carbon (except when bonded to a metal).
  The exceptions to this are C, CO, and CO2.
• Secondly, you must determine the type of bond
  that is in the given compound.

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Formula to Name Ionic

• If the compound contains an ionic bond, first
  look at the metal.
• Does the metal have more than one oxidation
  state?
• This can be found by looking at your periodic
  table in the box labeled oxidation for the metal
  at which you are looking.
• If no, then write the name of the metal as it
  appears on the periodic table.
• For example Na is sodium

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Formula to Name Ionic

• If the metal has more than one oxidation state,
  you must determine its charge in the given
  compound.
• For example Cu2O
• Oxygen always has a charge of 2 in ionic
  compounds, so each copper must have a charge of
  1 for this compound to have an overall charge of
  zero.
• Then write the name of the metal as it appears on
  the periodic table followed by its charge in
  Roman Numerals
• Cu2O is copper (I)

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Formula to Name Ionic

• Is there more than one type of non-metal in the
  given compound?
• If no, then write the name of the non-metal as
  given on the periodic table but change the ending
  of its name to ide.
• Examples
• Phosphorus becomes phosphide
• Oxygen becomes oxide
• Chlorine becomes chloride

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Formula to Name Ionic

• If there is more than one type of non-metal,
  then you have a polyatomic ion.
• A partial list of these can be located on your
  periodic table.
• Examples SO4 is sulfate, CO3 is carbonate, OH
  is hydroxide, etc.
• Once you find it on your periodic table, you
  simply write the name as given following the name
  of the metal.

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Formula to Name Ionic

• Lets try some out!
• NaCl
• sodium chloride
• PbS2
• lead (IV) sulfide
• MgOH
• magnesium hydroxide

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Formula to Name Ionic
Questions?
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Name to Formula Ionic

• Ionic compounds should be easy to recognize by
  their names as they should include the name of a
  metal followed by that of a non-metal or
  polyatomic ion.
• Examples
• copper (II) sulfide
• sodium hydroxide
• calcium phosphide

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Name to Formula Ionic

• First determine the symbol for and oxidation
  state of the metal named.
• Examples
• sodium hydroxide Na1
• calcium phosphide Ca2
• copper (II) sulfide Cu2
• Remember, if there is more than one possible
  oxidation state for the given metal, then look to
  the Roman Numeral following its name in the given
  formula to find its charge in the given compound.

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Name to Formula Ionic

• Once you know the symbol and charge of the metal
  in the given compound, look at the rest of the
  name.
• If the ending of the formula name is ide, then
  it is probably a single non-metal.
• The exception to this is hydroxide which is a
  polyatomic ion.

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Name to Formula Ionic

• Once you determine if it is a single non-metal
  you are looking for or a polyatomic ion, you must
  determine its symbol and charge.
• Examples
• sodium hydroxide OH1-
• calcium phosphide P3-
• copper (II) sulfide S2-

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Name to Formula Ionic

• Now that you know the symbols for and charges of
  the elements involved in the given compound, you
  can balance the charges.
• The correct formula for an ionic compound is
  that which contains the least amount of atoms
  necessary to make the overall charge of the
  compound zero.

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Name to Formula Ionic

• Lets balance the charges for our examples!
• Examples
• copper (II) sulfide Cu2 S2-
• CuS ? the charges are equal and opposite
• calcium phosphide Ca2 P3-
• Ca3P2 ? 3 Ca 6, 2 P -6
• sodium hydroxide Na1 OH1-
• NaOH ? the charges are equal and opposite

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Name to Formula Ionic

• Lets try some more!
• magnesium sulfate
• MgSO4
• chromium (III) chloride
• CrCl3
• manganese (II) nitride
• Mn3N2

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Name to Formula Ionic
Questions?
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Formula to Name Covalent

• If it is an inorganic compound, but contains a
  covalent bond instead of an ionic bond, then the
  process to name it is slightly different.
• The main difference is that you will be using
  prefixes to identify the quantity of each element
  in the compound.

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Formula to Name Covalent
Prefix of atoms Prefix of atoms
mono- 1 hexa- 6
di- 2 hepta- 7
tri- 3 octa- 8
tetra- 4 nona- 9
penta- 5 deca- 10
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Formula to Name Covalent

• Determine the name of the element belonging to
  the leftmost symbol in the compound.
• Look to the right of the symbol and see if there
  is a small number.
• If there is no number, then there is only one
  atom of that element.
• If there is a number, it denotes how many of
  that element is in the compound.

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Formula to Name Covalent

• Once you determine how many atoms of the element
  there are and the elements name, you can write
  the first part of the name.
• If there is only one atom of the element in the
  compound, then you just write the name of the
  element.
• If there is more than one atom of the element in
  the compound, then you use the appropriate prefix
  followed by the elements name.

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Formula to Name Covalent

• Examples
• NO
• nitrogen
• N2O
• dinitrogen
• SO
• sulfur
• S2O
• disulfur

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Formula to Name Covalent

• For the second element in the compound, the
  process is almost exactly the same.
• The only differences are that you use a prefix
  even if there is only one atom of the second
  element in the compound and you change the ending
  of the name like in ionic compounds.

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Formula to Name Covalent

• Lets try some!
• NO
• nitrogen monoxide
• N2O4
• dinitrogen tetraoxide
• SO2
• sulfur dioxide
• H2O
• dihydrogen monoxide

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Formula to Name Covalent
Questions?
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Name to Formula Covalent

• Due to the use of prefixes to denote the number
  of atoms of each element in a covalent compound,
  going from name to formula is actually pretty
  easy.
• Look at the first element named.
• If it does not have a prefix, then there is only
  one atom.
• If it has a prefix, then that is how many atoms
  there are.

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Name to Formula Covalent

• The second element in the formula name should
  always have a prefix to identify how many atoms
  there are.
• Simply look at the periodic table and find the
  non-metal which has a very similar name and the
  prefix will tell you how many there are.

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Name to Formula Covalent

• Lets try some!
• phosphorus trisulfide
• PS3
• disulfur dioxide
• S2O2
• silicon tetrahydride
• SiH4
• nitrogen monoxide
• NO

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Name to Formula Covalent
Questions?
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A Note on Naming Covalent Compounds

• There is one other type of covalent compound.
• Some non-metals do not exist in their element
  form, but instead in polyatomic molecules.
• There is a list of these non-metals on the back
  of your periodic table.

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A Note on Naming Covalent Compounds
Formula Name Formula Name
H2 hydrogen N2 nitrogen
Cl2 chlorine O2 oxygen
F2 fluorine Br2 bromine
I2 iodine As2 astatine
P4 phosphorus S8 sulfur
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A Note on Naming Covalent Compounds

• So, if you ever see the name of a non-metal
  alone and it is asking for the formula, check
  your list of polyatomic molecules first to make
  sure you have the formula correct.