Across
1
Second lightest element
3
Preserved remains of ancient life
7
Our home planet
8
Substance with pH below 7
10
Unit of force
12
Infectious microscopic agent
Down
2
Path of a planet around the sun
4
Particle of light
5
Substance with pH above 7
6
Solid with repeating atomic pattern
9
Measure of matter in an object
10
Nerve cell in the brain
11
Compound containing oxygen