text: why is mercury a liquid? other reason than molecular kinetic theory.? in the case of bromine it can be explained by covalent bonding theory, but i have yet found an explanation for the case of mercury. must be somethin special with its outer valence shell? just about everything in chemistry has to do with the outer valence shell.  this is no exception.  the metals in this row (period 6) basically bond with each other using their s and d orbitals.  as with everything else, this works best when you have 1 electron in each (e.g. h2) and worst when they're already full (e.g. he2).  mercury has them all (it's in column 12 = 2s + 10d), and therefore very poor bonding.  in constrast, tungsten (w) has half of them, and exceptional bonding (mp-3422 c), which is why it's used as the filament in light bulbs.  so why are cd and zn solids if they're the same column as hg?  it has to do mostly with the size (larger = further = weaker bonding), but is best described using band theory.  i'd recommend looking there.    p.s. things wierd when there are this many electrons in one atom, like yellow gold.