Weaknesses: Unfortunately for Boron the Moron, he does have one weakness; heat! If he gets overheated, he will melt. Arch Nemesis: Silver Stopper is his arch nemesis who conducts heat which is Boron the Moron’s weakness. Therefore, he avoids the superhero, Silver Stopper, at all costs. Suit: Aug 20, 2019 · Oxygen was the atomic weight standard for the other elements until 1961 when it was replaced by carbon 12. Oxygen made a good choice for the standard before much was known about isotopes because although there are 3 natural isotopes of oxygen, most of it is oxygen-16. This is why the atomic weight of oxygen (15.9994) is so close to 16.