Across
1
Nerve cell in the brain
4
Mass per unit volume
5
Particle of light
8
Infectious microscopic agent
10
Unit of heredity
11
Positive particle in nucleus
12
Icy body with a tail near the sun
Down
1
Center of an atom or cell
2
Push or pull on an object
3
Precious yellow metallic element
6
Glass that splits light into spectrum
7
Gas essential for breathing
9
Element found in all living things