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Chemical formulas are written with
rules according to the type of molecule.
Type 1: Binary Ionic
Between a metal and a non-metal and they�ll end with �-ide�
on the second word. The metal�s symbol and charge are
written, followed by the non-metals�s symbol and charge.
The charges are balanced by using coefficients to indicate
the number of atoms.
Type 2: Polyatomic Ionic
They either begin with �ammonium� or end with �-ate� or
�-ite� in the second word (except �hydroxide� and
�cyanide��those are polyatomic ions). A polyatomic ion is a
group of atoms that together have a charge. The metal�s
symbol and charge are written first (or ammonium, NH4+1, the
only polyatomic cation). The polyatomic anion�s symbols and
charge are written next. The charges are again balanced
with subscripts. If a subscript is added to a polyatomic
ion, use parenthesis around the ion.
Type 1 or 2 with Multivalent
Metals
They will have roman numerals in the name. Multivalent
metals are metals that have more than one possibility for
the charge. The charge of the metal is indicated with roman
numerals following the metal�s name. The formula is then
written following the rules for either Type 1 or Type 2.
Type 3: Binary Covalent
Between two non-metals. They will have use prefixes
indicated the number of atoms. �Mono-� is not used on the
first element. The element symbols are written, and the
prefixes indicate the subscript for each.
Type 4: Acids
The cation for an acid is H+. The anion is based on the
format of the name: �hydro___ic acids� end with a single
element; �___ic acids� end with the �___ate� polyatomic ion;
�___ous acids� end with the �___ite� polyatomic ion. Write
the correct anion�s symbol and charge and then balance the
charges with subscripts.
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