Across
1
Icy body with a tail near the sun
4
Center of an atom or cell
5
Positive particle in nucleus
9
Mass per unit volume
10
Tectonic landmass section
Down
2
Unit of energy
3
Path of a planet around the sun
6
Absolute temperature scale unit
7
Chemical element in table salt
8
Smallest unit of an element
11
Amplified beam of light