Here we present evidence that the gap between the highest occupied and lowest unoccupied molecular orbitals (HOMO–LUMO gap) can be tuned (1.12–1.89eV) by changing the Ga composition of Bi 3 Ga y anionic and neutral clusters, some of which display special stability. Collaboratively, mass spectrometry, photoelectron spectroscopy and computational results show that Bi3Ga2- is a very stable cluster with a large calculated HOMO–LUMO gap of 1.89eV, and can be viewed as a gas phase Zintl analogue of Sn52-, already synthesized in the solution phase. The stability of Bi3Ga2- is further attributed to the fact that it has 12 valence electrons and possesses a closo structure in agreement with Wade’s rules.