Which of the following inert (noble) gases is placed in period 4 of the periodic table?

1. Noble gases occupy group 18; each period ends with one. 2. Period 3 ends with Ar, period 4 with Kr, period 5 with Xe, period 6 with Rn. 3. So the period-4 noble gas is Krypton (Kr). _Source: RRB Group D CEN-02/2018 PYQ, Q.50._