What I'm getting from this is that -

  > under relativity fast things are heavier
  > electrons are fast, they actually have about a 23% weight boost
  > heavier electrons 'orbit' closer to the nucleus
  > the atomic size is then smaller than anticipated
  > this has a bunch of interesting effects on melting points, reactivity, colour/reflectivity etc, (especially of transition metals?)
  > this stuff has not always been well understood.

It's been a long time since I studied chemistry, so I may be reading it wrong. It's pretty cool though :)