Across
1
Positive particle in nucleus
3
Center of an atom or cell
5
Ball of burning gas in space
7
Basic unit of life
9
Compound containing oxygen
11
Element found in all living things
13
Unit of power
Down
2
Curved glass that refracts light
4
Unit of force
6
Infectious microscopic agent
8
Force that attracts objects together
10
Smallest unit of an element
12
Tissue that contracts for movement