Across
1
Center of an atom or cell
3
Positive particle in nucleus
5
Infectious microscopic agent
7
Precious yellow metallic element
10
Blocking of light by a celestial body
11
Mass per unit volume
12
Group of similar cells
Down
2
Chemical element in table salt
3
Glass that splits light into spectrum
4
Icy body with a tail near the sun
6
Reddish electrical conductor
8
Ball of burning gas in space
9
Preserved remains of ancient life