As more electrons are added to a 5n cluster, the number of electrons per vertex approaches 6. Instead of adopting structures based on 4n or 5n rules, the clusters tend to have structures governed by the 6n rules, which are based on rings. The rules for the 6n structures are as follows.
Example: S
:Electron count = 8 × S = 8 × 6 = 48 electrons.
:Since n = 8, 6n = 48, so the cluster is an 8-membered ring.
Hexane (CH)
:Electron count = 6 × C + 14 × H = 6 × 4 + 14 × 1 = 38
:Since n = 6, 6n = 36 and 6n + 2 = 38, so the cluster is a 6-membered chain.