Across
1
Path of a planet around the sun
4
Gas essential for breathing
6
Our home planet
8
Positive particle in nucleus
9
Ball of burning gas in space
10
Naturally occurring inorganic solid
11
Icy body with a tail near the sun
13
Substance with pH below 7
Down
2
Solid with repeating atomic pattern
3
Magnetic metallic element
5
Group of similar cells
7
Compound containing oxygen
12
Fourth state of matter