Promethium, radium, curium, and Californium are all radioactive enough to cause rectal damage. Conversely, I don't think phosphorus (black or red) or selenium are reactive enough to cause much harm.
I guess it's only implied but any liquid is inserted as a solid - e.i. below its melting point. It's assumed anything crumbly has a suitable binding agent.
A few of them are definitely wrong as has been pointed out to me but I'm glad we're all learning about science!