Identify the elements in the second, third, fourth, and fifth periods that have the same number of highest-energy-level electrons as barium.

Fill in the blanks for the following statements: the rms speed of the molecules in a sample of h2 gas at 300 k will be times larger than the rms speed of o2 molecules at the same temperature, and the ratio µrms (h2) / µrms (o2) with increasing temperature.