Across
1
Chemical element in table salt
5
Ball of burning gas in space
6
Icy body with a tail near the sun
9
Curved glass that refracts light
10
Gas essential for breathing
11
Center of an atom or cell
Down
2
Unit of electric potential
3
Path of a planet around the sun
4
Glass that splits light into spectrum
7
Nerve cell in the brain
8
Preserved remains of ancient life