When using chemical formula it is possible to calculate the percentage composition of the chemical. This can be useful when extracting metals from ores or when making fertilisers for specific ...

Its chemical formula is written as CO 2. You may be required to use a key to draw your own diagram of a molecule, eg: Using this key, the molecules SH 2 and NH 3 would be represented like this.

Dr Joe Hanson, a science writer based in Austin, Texas, worked out what a single 'human molecule' might look like if the chemical elements that make it up were written out.