2.7 Molecular Compounds:
Chemical Formulas and Naming
(Section 7.4 pg 192-196)
• Molecular compounds form covalent bonds, so we
don’t pay as much attention to ion charges – there
are different rules for naming & writing them.
• We are going to use a lot of prefixes:
• Don’t worry about memorizing these – they’re in
the Data Pages!!!
• To write the name of a molecular compound from
the formula, follow these steps:
– Make sure both elements are non-metals.
– Write the name of the first element with the correct
prefix (please note – if there is only ONE atom of the first
element, do not use ‘mono’ e.g. CO2 = carbon dioxide)
– Write the name of the second element with the correct
prefix.
– Change the ending of the second element to -ide.
– For example, C4S7 = tetracarbon heptasulfide
• To write the formula from the name, you simply
write down the symbol for each element and then
write an appropriate subscript for the number of
the prefix for each element.
• For example, triphosphorus octafluoride = P3F8