1The mixing bench
Tap an element in the table below to put it on the bench (the first tap fills the blue spot, the second fills the orange spot). On a computer you can also drag an element onto a spot. Tap a filled spot to empty it. Picking the same element twice shows the "self-pair", e.g. H + H = H₂.
Put two elements on the bench to see what the data says.
2The periodic table
Each square is one element: its symbol and its atomic number (how many protons it has). Colours show the element's family.
3Search
Type an element's name (sodium), symbol (Na) or number (11), or a formula from the data file (like NaCl or H2O). Write formulas with plain digits, H2O not H₂O.
4The whole picture: all 7,021 pairs
These totals are counted live from the embedded data file:
What the three statuses mean
Known compound: the file reports a record or an inference. Most records come from Wikidata; they can describe ions, clusters or transient species. Inferred self-pairs count the element itself, which is not a binary compound. A database match alone is not experimental confirmation.
Unknown: our database search found no record. That does not mean it's impossible. Many of these pairs, especially metal + metal, really do form alloys or compounds that the database simply doesn't list.
None known (dataset): the original file assigns this label using rules, often involving noble gases or very heavy elements. It is not a literature review and does not establish that no compound exists.
The raw evidence, source and notes remain visible below each pair. Generalized source notes may have exceptions: Na₂He, for example, is a reported high-pressure compound. Bond labels are family-based heuristics, not calculated bonds.
5Challenges
Put elements on the bench, then press Check. Each answer is checked against the data file.