Across
1
Smallest unit of an element
3
Biological catalyst
4
Our home planet
5
Nerve cell in the brain
6
Tectonic landmass section
9
Preserved remains of ancient life
10
Element found in all living things
11
Blocking of light by a celestial body
Down
2
Gas essential for breathing
6
Glass that splits light into spectrum
7
Hottest planet in solar system
8
Ball of burning gas in space
12
Substance with pH below 7