Across
1
Naturally occurring inorganic solid
6
Force that attracts objects together
7
Group of similar cells
9
Second lightest element
12
Nerve cell in the brain
Down
2
Magnetic metallic element
3
Unit of electric potential
4
Biological catalyst
5
Positive particle in nucleus
8
Gas form of a liquid
10
Disturbance that transfers energy
11
Infectious microscopic agent
13
Center of an atom or cell