Across
1
Preserved remains of ancient life
3
Unit of heredity
5
Blocking of light by a celestial body
7
Chemical element in table salt
8
Tectonic landmass section
10
Smallest unit of an element
Down
2
Nerve cell in the brain
4
Gas essential for breathing
5
Biological catalyst
6
Magnetic metallic element
9
Solid with repeating atomic pattern
11
Basic unit of life
12
Absolute temperature scale unit
13
Second lightest element