Across
1
Path of a planet around the sun
3
Element found in all living things
5
Blocking of light by a celestial body
6
Measure of matter in an object
12
Gas essential for breathing
Down
2
Solid with repeating atomic pattern
4
Smallest unit of an element
7
Basic unit of life
8
Curved glass that refracts light
9
Infectious microscopic agent
10
Ball of burning gas in space
11
Substance with pH above 7