Dichotomous Key for Naming Compounds from their Formulas
1a. The first element in the formula is a non-metal (from right hand side of periodic table – shaded) = Covelent/Molecular
1b. The first element in the formula is a metal (from the left and middle of the periodic table- unshaded)= See #2
Covalent Molecular = Look at the subscripts after each
element symbol and place the corresponding prefix in front
of its name (no mono on first). Do not simplify the ratio!
Change the ending of the second element to ide.
2a. The first element in the formula is the H+ ion = Acid = See #6
2b. The first element in the formula is not the H+ ion = See #3
3a. The first element in the formula has only one possible combining capacity= See #4
3b. The first element in the formula has more than one possible combining capacity = See #5
4a. The second part in the formula is not a polyatomic ion (has only one element in the ion)= Binary Compound - Name the metal + Non-metal with ide ending
4b. The second part in the formula is a polyatomic ion (has more than one element in the ion)= See #6 Polyatomic Compound - Name metal + polyatomic name
5a. The second element in the formula is not a polyatomic ion (more than one element in the ion)= Multivalent Compound
5b. The second element in the formula is a polyatomic ion (has more than one element in the ion)=Multivalent Polyatomic Compound
6a. The second part in the formula is not a polyatomic ion = Hyro
6b. The second part in the formula is a polyatomic ion = see #7
7a. The polyatomic ion end in ate =
ic acid
7b. The polyatomic ion ends in ite =
ous acid
REMEMEBER: NO CAPITAL LETTERS IN THE NAMES!!!
ic acid
Multivalent Compound – You have to work backwords using
the criss-cross rule to determine the c.c. of the metal. When
you right the name put the c.c. in roman numerals in
brackets after the metal name then the non-metal ending in
ide.
Multivalent Polyatomic – same as above but second part of
name is the polyatomic name from the table.
Dichotomous Key for Writing Formulas from their Names
1a. The name has pre-fixes in it = Covelent/Molecular – use the prefixes to determine the subscripts after each element. Do not simplify the ratio!
1b. The name does not have pre-fixes in it = See #2
2a. The name has acid at the end = Acid = See #6
2b. The name does not have acid in it = See #3
3a. There are no roman numerals after the first name= See #4
3b. There are roman numerals after the first name = See #5
Polyatomic Compound = Same as Binary compound but put a
bracket around the polyatomic ion if their is a subscript after
it!.
4a. The second part of the name ends with ide = Binary Compound – Write down the ions then use the criss-cross rule and simplify the ratio
4b. The second part of the name does not end with ide = See #6 Polyatomic Compound
5a. The second part of the name ends with ide = Multivalent Compound
5b. The second part of the name does not end with ide =Multivalent Polyatomic Compound
Multivalent Compound – The roman numeral after the metals name
tells you its c.c. Write down the two ions then use the criss-cross rule
and simplify the ratio.
Multivalent Polyatomic – same as above but second part of the formula
is from the polyatomic table. Put a bracket around the polyatomic ion if
their is a subscript after it!.
6a. The name starts with hydro = Hyro
ic acid = Hydrogen ion with non-metal ion from periodic table. Use criss cross rules and simplify the ratio.
6b. The name does not start with hydro = see #7
7a. The name is in the form
ic acid = Hydrogen ion with polyatomic ion ending with ate. Use criss cross rules and simplify the ratio. Put a bracket around the
polyatomic ion if their is a subscript after it!.
7b. The polyatomic ion ends in ite =
ous acid = Hydrogen ion with polyatomic ion ending with ite. Use criss cross rules and simplify the ratio. Put a bracket
around the polyatomic ion if their is a subscript after it!.