Why are the subscripts in a chemical formula whole numbers (for example, N2O5 instead of NO2.5)?

1 Answer
Truong-Son N.
Oct 2, 2016

Because it doesn't make sense to have half an atom. NO2.5, which we could call a "pseudo-formula", implies you have (two and a) half oxygen atoms for every molecule of "NO2.5", which is physically impossible. So, we scale to whole numbers and rewrite as N2O5 instead.

Same thing with something like C1.5H4O0.5. We instead write C3H8O.

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