As it turns out, the possibility of creating Kryptonite isn’t possible, so if Superman ever does invade, we’re screwed.
The boffins over at iO9 have the chemistry worked out. As we have the element krypton, and molecules which end in ‘ite’, surely combining the two would result in kryptonite?
According to the site, each part of the name – in this case ‘kryton’ and ‘ite’ – tells us something about what it is and what it does. The name ‘kryptonite’ indicates that the molecule is an oxyanion (a negatively-charged molecule with several oxygen atoms attached).
“Most of the time, when you hear about these oxyanions,” writes Esther Inglis-Arkell “you hear about ‘ates’ not ‘ites.’ Nitrate (potassium nitrate makes smoke bombs) is NO3- , sulfate (potassium sulfate makes fertilizer) is SO42-, and carbonate (calcium carbonate is in shells and chalk) is CO32-. “Ites” have the same negative charge as “ates,” but have one less oxygen atom. So nitrite is NO2-, and sulfite is SO32-.”
You see, kryptonite contains no oxygen atoms, nor does it carry a charge. As krypton is a gas, it doesn’t combine with oxygen. Until 1960, scientists didn’t believe it could combine with anything whatsoever. It wasn’t until someone was able to combine krypton with fluorine that we knew it could be, and it takes a temperature of −183 °C to even enable the merging of the two.
So if fluorine is the only chemical element that can be combined with krypton, that means there is no way - at the moment - of making kryptonite. Sorry.
Subject: Here's The Scientific Logic Behind Why Kryptonite Can't Exist 
