Color print 1280 X 960 GIF B & W print Tutorial back Values table Symbol key Tutorial next It is to be remembered that the idealized model of the Bohr hydrogen atom, where a single electron orbits a single, immobile proton like a planet around a sun, has been replaced with a model which more aptly fits experimental evidence. While much of the nomenclature from that model is still in use, one notable exception involves h-bar, [hB] in GDA use, now spoken of more often as the atomic unit of action than as the atomic unit of angular momentum.