IIRC, Radon hasn't been proven to be a noble gas. Xenon is downright promiscuous compared to the other noble gases, and some chemists think that trend continues into radon.
People across the board think that they will never need any math or science after leaving school. That's how you get jokes that anyone who was not asleep in physics would not have created.
It extinguishes the stars it forms in. Once you have enough Iron, and the amount is actually quite small compared to the rest of the mass of the star, that triggers a nova. This is due to Iron needing extra energy to either fuse or fission.
Close, the maximum binding energy per atomic mass unit is iron-56, but splitting heavier atoms does not guarrentee releasing energy. If you consider the graph of specific bonding energy against atomic mass, then also consider that you need two numbers that add up to the original mass, it is clear that you need approximately more than 100u to release energy on fission.