Across
1
Second lightest element
4
Element found in all living things
5
Disturbance that transfers energy
7
Smallest unit of an element
Down
2
Substance with pH above 7
3
Fourth state of matter
6
Unit of force
8
Center of an atom or cell
9
Reddish electrical conductor
10
Blocking of light by a celestial body
11
Group of similar cells
12
The Red Planet