Across
1
Positive particle in nucleus
3
Second lightest element
4
Measure of matter in an object
5
Smallest unit of an element
9
Unit of electric potential
Down
1
Particle of light
2
Biological catalyst
3
Form of thermal energy
6
Reddish electrical conductor
7
Tissue that contracts for movement
8
Ball of burning gas in space
10
Substance with pH below 7