Across
1
Reddish electrical conductor
4
Magnetic metallic element
5
Group of similar cells
6
Fourth state of matter
7
Basic unit of life
8
Disturbance that transfers energy
13
Curved glass that refracts light
Down
2
Ball of burning gas in space
3
Blocking of light by a celestial body
6
Positive particle in nucleus
9
Force that attracts objects together
10
Measure of matter in an object
11
Compound containing oxygen
12
Amplified beam of light