What element has 2 valence electrons and 3 energy levels?

Explanation:

I think Lithium is the answer but I'm not positive it's the best answer I could find sorry

water is used to store them because it would keep the radiation from getting out in the open and causing harm to the workers

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.