Regex for Finding Radioactive Elements
Char Count 61

lon|ct|oh|^ra|...t.+i|^c?u|or.+u|r.+c.|e..+e|f.?e|^h?as|be*.i


One 3 characters better than accepted answer!

63-character solution found with Peter Norvig's Regex golf solver. 61-character improvement found by a personal rewrite of that program in Go.