Chlorine and element X have similar chemical properties. An atom of element X could have an electron configuration of
(1) 2-2 (2) 2-8-1 (3) 2-8-8 (4) 2-8-18-7
(1) 2-2 (2) 2-8-1 (3) 2-8-8 (4) 2-8-18-7