Across
1
Gas essential for breathing
4
Path of a planet around the sun
7
Second lightest element
8
Amplified beam of light
11
Positive particle in nucleus
Down
2
Unit of heredity
3
Magnetic metallic element
5
The Red Planet
6
Naturally occurring inorganic solid
9
Center of an atom or cell
10
Substance with pH below 7
12
Unit of force