Across
1
Gas essential for breathing
5
Tectonic landmass section
6
Center of an atom or cell
7
Compound containing oxygen
8
Chemical element in table salt
9
Curved glass that refracts light
12
Unit of electric potential
13
Precious yellow metallic element
Down
2
Force that attracts objects together
3
Biological catalyst
4
Preserved remains of ancient life
5
Particle of light
10
Natural satellite of Earth
11
Element found in all living things