Across
1
Natural satellite of Earth
4
Gas essential for breathing
7
Unit of power
8
Second lightest element
10
Precious yellow metallic element
11
Unit of heredity
Down
2
Mass per unit volume
3
Gas form of a liquid
5
Icy body with a tail near the sun
6
Center of an atom or cell
9
Blocking of light by a celestial body
12
Unit of energy