Across
1
Center of an atom or cell
4
Unit of energy
5
Reddish electrical conductor
7
Push or pull on an object
9
Curved glass that refracts light
12
Particle of light
Down
2
Chemical element in table salt
3
Unit of force
6
The Red Planet
7
Preserved remains of ancient life
8
Force that attracts objects together
10
Positive particle in nucleus
11
Basic unit of life