Across
1
Reddish electrical conductor
4
Smallest unit of an element
5
Center of an atom or cell
7
Blocking of light by a celestial body
10
Disturbance that transfers energy
Down
2
Absolute temperature scale unit
3
Positive particle in nucleus
6
Biological catalyst
8
Substance with pH above 7
9
Precious yellow metallic element
11
Group of similar cells
12
Nerve cell in the brain
13
Curved glass that refracts light