Across
1
Positive particle in nucleus
4
Smallest unit of an element
6
Group of similar cells
10
Naturally occurring inorganic solid
12
Amplified beam of light
13
Blocking of light by a celestial body
Down
2
The Red Planet
3
Unit of electric potential
5
Our home planet
7
Nerve cell in the brain
8
Center of an atom or cell
9
Tectonic landmass section
11
Second lightest element