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