Question

which is the most rare element

Answer 1

there are many rare element but according to me most rarest is silicon

Answer 2

most rarest element on earth is astatine . Astatine is a naturally occurring semi-metal that results from the decay of uranium and thorium. In its most stable form - astatine-210 - it's got a half-life of just 8.1 hours, which means even if you did happen to stumble on some of it, half of it would be gone by the end of a work day. Depending on how it decays, it'll either turn into the isotopes bismuth-206 or polonium-210.