 So I'm just going to go through and run through the exceptions again just to remind you. We had the electron deficient atoms which are beryllian and boron. We had the hypervalent atoms which are the atoms in period 3 and below which are able to take more than 8 electrons in their outer shell but you should always try for 8 electrons as a first point of call. Go for 8 electrons as the default and if you can't make the structure by restricting them to 8 then you can give them more. And finally we have the atoms that must have a noble gas configuration which are hydrogen which needs 2 and carbon, nitrogen, oxygen and fluorine which all need 8. So I'd like you to try drawing these four molecules, drawing the Lewis structures for these four molecules. We've got oxygen gas which you use for breathing, we've got bromomethane which used to be used as a soil sterilization agent in agriculture but was banned in 1999 because it contributed to the degradation of the ozone layer. We've got sulfur hexafluoride which is a really dense and unreactive gas and if you search on YouTube you'll find a bunch of really cool videos that show just how much denser than air it actually is. And we've got methanol also known as formaldehyde which has often been used as an embalming or preserving agent for flesh or biological specimens.