<Tr> <Td> element by radioactive decay </Td> </Tr> <Tr> <Td> Atomic number color: red = gas </Td> </Tr> <Tr> <Td_colspan="2"> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul>

Who discovered the rest of the inert gases... noble gases