A type of stability that is the analogue for fullerenes and polyhedral boranes of Hückel’s rule for planar aromatic molecules. This stability is also known as Hirsch’s rule because Andreas Hirsch (1960–) and his colleagues predicted in 2000 that fullerenes would be stable if they had $2{\left(n+1\right)}^2$ pi electrons where n is a non-negative integer. There are extensions and modifications of Hirsch’s rule.