Whilst clusters of carbon atoms are well-known, my eye was caught by a recent article describing the detection of a cluster of boron atoms, B<sub>40</sub> to be specific.[1] My interest was in how the σ and π-electrons were partitioned. In a C<sub>40</sub>, one can reliably predict that each carbon would contribute precisely one π-electron. But boron, being more electropositive, does not always play like that.