Describe the bonding in a tribromide anion, what is its structure? I'm thinking it will be linear with a negative charge on the middle bromine. Someone told me it is trigonal bipyramidal geometry with 3 lone pairs around the central bromine and the two other bromines above and below making it linear. Is this correct? Also is it just covalent bonding in the molecule?
In fact, tribromide ion has the generic formula $\ce{AX2E3}$ according to Lewis diagram. Where  $\ce{A}$ is the central atom, $\ce{X}$ an atom bonded to $\ce{A}$ and $\ce{E}$ a lone pair on $\ce{A}$.  Using Valence Shell Electron Pair Repulsion (VSEPR) theory,  the geometry  of this ion will be
 :


So, the molecular shape is linear, while the electron pair geometry is trigonal  bipyramid.
 And the bonds in the ion are covalent.