Hi,
A chemical problem: I would like to be able to count the number of heavy atoms from chemical formulas. As an example, the formula C5H8N2OF contains 9 heavy atoms (anything other than hydrogen). Relevant heavy atoms are: C, N, O, S, F, Cl, Br and I.
Any help with coding this in Excel would be appreciated!
Pennypacker
You might need to break that down for the non-chemists...
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Hi Pennpacker,
Find the attached with a few helping columns to get your Heavy Answer.
Hope this works for you. If not then it should give you a start on a better formula.
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What are you defining as "Heavy Atoms", it was my understanding that Iodine was the only heavy atom in your given list, maybe things have changed since my day.
A few more example formulae would be an advantage, perhaps if you were to provide a sample workbook with a couple of dozen examples and the expected results, we might be able to provide a more definitive solution.
In the meantime, try this UDF
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I have left a formula in this attachment, but I think it over simplifies the situation, as does to a lesser extent the UDF as it stands.
I have added a few random molecular formulae to illustrate the point.
The final solution will probably involve comparing the given formula to the entire periodic table, and even then a bit more "tweeking" will be required.
If you need any more information, please feel free to ask.
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Hi. Very useful script above. Just to clarify, what I believe is meant by "heavy atoms" is "non-hydrogen atoms".
The above code appears to work, except for cases when there is more than one digit representing the number of atoms.
For example, the script works with "C6H12O6" (# heavy atoms = 12), but not with "C12H24O12" (# heavy atoms = 2, whereas the correct answer is 24.) I have extended the script so that it works correctly with two digit numbers. My modifications to the script are not very elegant (disclaimer, I have never coded in Visual Basic before), but it seems to work.
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