Hückel's rule helps us know which molecular orbital, bonding or antibonding contains more electrons, and it is derived from the same. And on the basis of this, we can find out the stability of the compounds.
But, this rule was specifically introduced for cyclic organic compounds to know if they are aromatic or not. But again, the reasoning remains the same across all compounds, that is, if more electrons are in BMO than in ABMO – stable; otherwise not.
So, I was wondering why we couldn't use the same rule for cyclic inorganic compounds? I don't know, but I might be missing out somewhere. Any help would be appreciated.
Also: This pdf here, agrees that Hückel's rule can be applied to inorganic cyclic compounds, but with a 'maybe'.
Whereas organic compounds need to be planar to be aromatic, no such limitation applies to inorganics. An inorganic compound may be expected to be aromatic if it satisfies a “counting rule”; the familiar Hückel rule applies to planar aromatics and the Hirsch rule works for spherical analogs.