Across
1
Blocking of light by a celestial body
4
Smallest unit of an element
5
The Red Planet
7
Nerve cell in the brain
10
Unit of force
13
Chemical element in table salt
Down
2
Gas essential for breathing
3
Disturbance that transfers energy
6
Compound containing oxygen
7
Center of an atom or cell
8
Push or pull on an object
9
Preserved remains of ancient life
11
Path of a planet around the sun
12
Second lightest element