CHEMISTRY COMMUNITY

how do you figure out the shape from a formula?
ex: [Co(en)2(Br)2]
it is octahedral but why?

Ethylenediamine is bidentate, so it can form two bonds. Because there are two of these and two bromine attached to Cobalt, there are six bonds total. This gives a VSEPR formula of AX6, which is octahedral.