Given a set of atoms, I would like to find (some / the most common) molecules that include only (some/all) atoms of the set. Is there any online search engine that can do this?

E.g. Atoms={C,H} --> Molecules={CH$_4$, C$_2$H$_6$, ...}


  • I am looking for known molecules.
  • It is OK if I can only find chemical formulae, so without all possible configurations.
  • 4
    $\begingroup$ Personally, I doubt so because there are literally millions, if not billions, of compounds that contain C and H (or any combination of atoms that you specify, unless it's something esoteric like Zr, N, Se). $\endgroup$ Commented Feb 10, 2016 at 22:20
  • 1
    $\begingroup$ Is there some database where you could enter a formula like $C_aH_bO_c$ and get molecules ( compounds) that fit (where a,b and c are given integers)? Certainly by the time that you get to 100 carbons there are more unknown possible compounds than known ones. $\endgroup$
    – MaxW
    Commented Feb 10, 2016 at 22:38
  • $\begingroup$ Pft, you can even check Wikipedia for compounds containing specific elements. $\endgroup$
    – Mithoron
    Commented Feb 10, 2016 at 23:17
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    $\begingroup$ You can search ChemSpider using a formula for one... chemspider.com/… $\endgroup$
    – MaxW
    Commented Feb 11, 2016 at 3:23
  • $\begingroup$ I'm pretty certain the question here is about searching known molecules, not theoretical ones. There are millions of connected chemical-like graphs with formula N3O4P5 yet I doubt very much that many of them correspond to stable chemical structures! $\endgroup$
    – gilleain
    Commented Feb 11, 2016 at 10:02

1 Answer 1


You can use ChemSpider's full search:


and click on the 'Elements' section. Alternatively, there is a direct link here:


This gives you two periodic tables that you can select elements from for your search. I think the upper one is 'allowed' and the lower one is 'forbidden', but I haven't tested this.

Of course, as pointed out in the comments, the set {C, H} will give you most of the database! However, for rarer elements this can be a better filter.


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