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Except pure alloys, are there any compounds with more metal elements in proportion of atoms than nonmetal elements in proportion of atoms?

For example, Aluminium oxide has 2 metal elements & 3 nonmetal elements. Do we have a compound with X metal elements & Y nonmetal elements, where Y is more then X.

user2986288
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  • Pure alloys have no nonmetals, so we do not count them. – user2986288 Feb 24 '15 at 00:57
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    It's proportion of atoms of elements... Your asking about Na2O, Li3N and other compounds like that? Please ask precisely - it seems that this answer could have been closed as imprecise. – Mithoron Feb 24 '15 at 01:00

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There are some rare but very interesting cases in which two metals react when mixed instead of forming an alloy, creating a non-metallic compound made only with metal atoms. Examples are caesium auride ($\ce{CsAu}$), caesium platinide ($\ce{Cs2Pt}$) and several barium platinides ($\ce{BaPt}$, $\ce{Ba2Pt}$, $\ce{Ba3Pt2}$, and possibly others), all of which best described as ionic salts rather than alloys. These are a remarkable consequence of relativistic effects in heavy atoms.

Nicolau Saker Neto
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  • They are not rare, they are rarely discussed in common chemistry. – permeakra Feb 24 '15 at 02:32
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    @permeakra Really? Those are just about the only ones I know. Could you provide some more examples? I'd be curious to look them up. – Nicolau Saker Neto Feb 24 '15 at 02:34
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    Let me put it this way: there is a significant amount of known solid phases with most atoms having high coordination numbers and having non-trivial stochiometry. Some of them exhibit metallic conductivity, some do not. Most of them are united under 'umbrella term' 'intermetallics', but a lot of borides, carbides, silicides and nitrides follows similar rules. Since the family includes exclusively solid state compounds they are hard to study and classify, so there is very little easily googleable info on them. – permeakra Feb 24 '15 at 02:59
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    As typical examples: $\ce{Fe3C, Fe3Si, FeSi, FeSi2, TiN_{1-x}}$ as having obvious practical use. Less known, but also significant $\ce{Ni3Al, Nb3Sn}$. A lot of obscure phases guarded by packing. – permeakra Feb 24 '15 at 03:11
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    Again, the compounds alone seem to be pretty common, a lot of metal pairs and triples raise several solid phases. However, most of them have little practical applications and so the field is not widely known, especially since they are mostly 'synthesized' by alloying and detected by X-ray phase analysis. – permeakra Feb 24 '15 at 03:14
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    Still, some phases can be dissolved in liquid ammonia (AFAIK, some phases with $\ce{Pb, Bi}$-containing polyhedral 'aniones'). – permeakra Feb 24 '15 at 03:19
  • Thank you for the information, I like having my worldview expanded! I had thought the examples I cited were uniquely ionic among intermetallics, but indeed the field seems so vast as to contain many cases like you cite. I also hadn't read about Zintl ions in a long while, so I forgot about those; even if monoatomic metallic anions are rare and presumably difficult to stabilize in a simple binary/ternary solid, anionic metallic clusters are not so limited. – Nicolau Saker Neto Feb 24 '15 at 03:37
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In addition to the answers by Nicolau and DrMoishe.

Most prominent examples are the binary oxides of the alkali metals $\ce{A2O}$: lithium oxide $\ce{A~=~Li}$, sodium oxide $\ce{A~=~Na}$, potassium oxide $\ce{A~=~K}$, rubidium oxide $\ce{A~=~Rb}$ and caesium oxide $\ce{A~=~Cs}$.
Of course there are also higher homologs of these compounds like lithium sulfide $\ce{Li2S}$.

Especially for rubidium and caesium there are also a number of suboxides, i.e. $\ce{A9O2}$ and others. This is a whole class of compounds whith a rich variety.

There are also the nitrides of the alkali and earth alkali metals, e.g. lithium nitride $\ce{Li3N}$ and magnesium nitride $\ce{Mg3N2}$.

There are a couple of phosphides known, that fit your description, e.g. $\ce{K3P}$, $\ce{K4P3}$, $\ce{K5P4}$. These compound are also known from transition metals, like $\ce{Cu3P}$ or $\ce{Ni5P2}$.

Like the above, there are also some very common carbides, like aluminium carbide $\ce{Al4C3}$.

And I am very certain, there are many more.

Oscar Lanzi
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Martin - マーチン
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Sure, e.g. sodium aluminate, Na2Al2O4 (anhydrous formula), is a common chemical (it's the "gray stuff" on aluminum dishware cleaned in an automatic dishwasher with alkaline detergents).

DrMoishe Pippik
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Petzite, $\ce{Ag3AuTe2}$, is an uncommon telluride containing mineral that seems to fit the bill.

Sodium oxide $\ce{Na2O}$ is well known, as is potassium oxide, rubidium oxide, etc.

Some one should write a parser and see if this list from Wikipedia has any more examples. I didn't see any that weren't already mentioned here on a quick skim.

Curt F.
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