Across
1
The Red Planet
3
Positive particle in nucleus
4
Center of an atom or cell
10
Unit of energy
11
Magnetic metallic element
Down
1
Measure of matter in an object
2
Ball of burning gas in space
5
Substance with pH above 7
6
Chemical element in table salt
7
Nerve cell in the brain
8
Gas essential for breathing
9
Substance with pH below 7