roentgenium, artificially produced radioactive chemical element is called eka gold Its atomic number is 111 It is inert to air, but the element is generally unstable. It is 11 th group element (1B) Solution roentgenium, artificially produced radioactive chemical element is called eka gold Its atomic number is 111 It is inert to air, but the element is generally unstable. It is 11 th group element (1B).