Question

how huckel rule help to deside the aromatic character of a compound?

Answer 1

I believe it said that if a cyclic, planar molecule had: 4n+2\(\pi\)e\(^-\) than it was considered aromatic.
So, obvi, you start by counting the # of \(\pi\) e\(^-\) in the molecule or whatever it is you're using to test. Then, set that # = 4n+2 and solve for \(\sf \color{red}{n}\). If its 0 or any positive integer, then teh rule has been met.

For instance, benzene has 6, so 4n+2 = 6, solving for, \(n\), you get \(\sf \color{orange}{1}\). Which is a positive integer value, and hencforth benzene is aromatic by hückels rule.