We investigated the electronic structure and chemical bonding of the B3 −, Al3 −, and Ga3 − anions, and the gas phase NaB3, NaAl3, and NaGa3 molecules. We found that the ground state of the neutral gas phase salts contains an equilateral triangular anion interacting with a Na+ cation. The B3 −, Al3 −, and Ga3 − anions possess two delocalized π electrons and are found to be aromatic. The triangular anions have been shown to be related to recently synthesized organometallic compound containing an aromatic -Ga3 2− unit, but they are differ from them by four valence electrons. The reason for earlier appearance of the π-orbital in the B3 −, Al3 −, and Ga3 − anions is discussed.