Across
1
Second lightest element
3
Basic unit of life
5
Amplified beam of light
6
Reddish electrical conductor
8
Center of an atom or cell
10
Blocking of light by a celestial body
11
Natural satellite of Earth
12
Unit of heredity
Down
2
Tectonic landmass section
4
Group of similar cells
7
Compound containing oxygen
9
Push or pull on an object