Preview question: Indica el elemento que falta en el grupo: He, Ne, Ar, Kr, Xe, {1:SHORTANSWER:=Rn}

Behaviour being used: Adaptive mode

Minimum fraction: 0

Question summary: Indica el elemento que falta en el grupo: He, Ne, Ar, Kr, Xe, _____

Right answer summary: part 1: Rn

Question state: todo