Are metal molecules actually molecules?

[Adam]

Are metal "molecules" actually molecules?

As the title asks. Are things like FeC actually molecules? The way I read the defintions, a compound is a molecule consisting of more than one element. Metals are capable of more than one type of bonding. We can reduce any metal to a small group of atoms representing the whole. Can we correctly call such a group a molecule?

 

[suyver]

I would say no, because you cannot make a molecule of FeC. This material exists, but only as a solid / crystal consisting of billions and billions FeC units. An FeC 'molecule' would have several unpaired electrons and be extremely unstable if you could ever make it.

 

[Adam]

However, we know some metals form molecules. NaCl.

 

[FZ+]

IIRC, molecules refer specifically to compounds bonded covalently - ie. with electrons shared, rather than transferred. I think most metal compounds fall on this account. Though there are exceptions eg. beryllium.

 

[Adam]

What does Beryllium do that's odd?

 

[GCT]

As the title asks. Are things like FeC actually molecules? The way I read the defintions, a compound is a molecule consisting of more than one element. Metals are capable of more than one type of bonding. We can reduce any metal to a small group of atoms representing the whole. Can we correctly call such a group a molecule?

What do you mean? Metals can be pure metals (consisting of only one element) or it can consist of different impurities. We use the term molecules primarily to describe covalent compounds, or rather compounds that involve molecular orbitals such as organic compounds, compounds with similar electronegativity where electrons are shared. Do ionic compounds have molecular orbitals? No. Molecular orbitals are associated with atomic orbitals, hybrid orbitals, and the combination thereof.

 

[FZ+]

What does Beryllium do that's odd?

Beryllium is both tiny, and forms 2+ positive ions. This high charge/size ratio attracts electron density from the negative ion, giving the bond covalent character. This means that beryllium's chemical properties are very different from the other members of it's group.

 

[red_fox77]

Beryllium also expands when it freezes if I remember correctly, and is the only element to do so. Water does the same as you know; but pretty much everything else will get smaller. Doesn't really have anything to do with this discussion, but thought I would mention it.

 

[shrumeo]

OK, NaCl is NOT a molecule.

It is the same case as FeC, a network material. The empirical formula is simply a convenience and does not denote any molecular structure.

And Be is not ALL THAT different from Al.
They both can survive with 6 valence electrons. But, Al doesn't do it very often. Al complexes (molecules) will often dimerize to attain the old octet.

Good old general chemistry!

Now, metals, of course, will be a part of a molecule (as in a neutral, covalently bound species). There are countless neutral metal complexes, and even if the complexes are ions, while in solution they can be considered "molecular" if you will.