Across
1
Center of an atom or cell
3
Path of a planet around the sun
6
The Red Planet
8
Compound containing oxygen
10
Natural satellite of Earth
13
Substance with pH above 7
Down
2
Push or pull on an object
3
Gas essential for breathing
4
Second lightest element
5
Infectious microscopic agent
7
Substance with pH below 7
9
Nerve cell in the brain
11
Precious yellow metallic element
12
Tissue that contracts for movement