Across
1
Path of a planet around the sun
3
Fourth state of matter
5
Icy body with a tail near the sun
6
Precious yellow metallic element
7
Chemical element in table salt
10
Our home planet
Down
2
Smallest unit of an element
4
Molten rock beneath Earth surface
8
Gas essential for breathing
9
Center of an atom or cell
11
Substance with pH above 7