Across
1
Second lightest element
4
Gas essential for breathing
5
Biological catalyst
8
Amplified beam of light
9
Naturally occurring inorganic solid
11
Positive particle in nucleus
Down
2
Unit of energy
3
Magnetic metallic element
5
Blocking of light by a celestial body
6
Reddish electrical conductor
7
The Red Planet
10
Substance with pH above 7