which is larger in size chlorine or fluorine

Chlorine is larger in size than fluorine because on moving down the group the extrashell is addded which increases the size of the atom.Also since fluorine has its valence electrons in the n=2 energy level, and since chlorine has its valence electrons in the n=3 energy level.The shell having last electron enters in 2 for fluorine whereas in chlorine it enters into 3^rd shell