Across
1
Gas form of a liquid
3
Mass per unit volume
5
Smallest unit of an element
8
Particle of light
12
Unit of energy
14
Preserved remains of ancient life
Down
2
Our home planet
4
Element found in all living things
6
Magnetic metallic element
7
Second lightest element
9
Blocking of light by a celestial body
10
Substance with pH below 7
11
Chemical element in table salt
13
Nerve cell in the brain
15
Positive particle in nucleus