Across
1
Smallest unit of an element
4
Biological catalyst
7
Unit of energy
9
Amplified beam of light
10
Force that attracts objects together
11
Particle of light
Down
2
Positive particle in nucleus
3
Second lightest element
5
Group of similar cells
6
Tissue that contracts for movement
8
Unit of electric potential
9
Curved glass that refracts light