Across
1
Force that attracts objects together
2
Unit of force
5
The Red Planet
7
Tissue that contracts for movement
8
Positive particle in nucleus
9
Our home planet
Down
2
Nerve cell in the brain
3
Smallest unit of an element
4
Unit of power
6
Center of an atom or cell
10
Hottest planet in solar system
11
Element found in all living things
12
Second lightest element
13
Form of thermal energy