Across
1
Reddish electrical conductor
4
Second lightest element
7
Nerve cell in the brain
9
Unit of energy
10
Unit of power
11
Mass per unit volume
Down
2
Our home planet
3
Positive particle in nucleus
5
Biological catalyst
6
Group of similar cells
8
Element found in all living things
12
Path of a planet around the sun
13
Measure of matter in an object