Across
1
Gas essential for breathing
5
Smallest unit of an element
6
Second lightest element
7
Blocking of light by a celestial body
9
Naturally occurring inorganic solid
Down
2
Natural satellite of Earth
3
Solid with repeating atomic pattern
4
Biological catalyst
8
Icy body with a tail near the sun
10
Infectious microscopic agent
11
Disturbance that transfers energy
12
Basic unit of life
13
Fourth state of matter