(i) (ii) (iii) (iv) (v) (vi) (vii) The number of compounds/species which obey Huckel's rule is _____

Step-by-step solution

Criteria for Huckel’s rule: (i) Planarity-The molecule must be planar. (ii) Complete delocalisation of π electrons (iii) Presence of (4n + 2)π electrons in ring where n is an integer (n = 0, 1, 2, …). If the molecule has a number of π electrons that satisfies this rule, then it is considered to be aromatic. If the number of π electrons does not satisfy this rule, then the molecule is considered to be non-aromatic. The compounds which follow Huckel’s rule are: