When looking at periods, which of the following are increasing?

Reactivity

Atomic Mass

Energy Level

None

Energy level

Explanation:

Periods in the periodic table are arranged in rows. Each row indicates a new period. For example, period 1 starts at the top and consist of only two elements, Hydrogen (H) and Helium (He).

The periods indicate the highest energy level of the elements that fall in the same row. So as the period increases, the energy level increases.