Across
1
Precious yellow metallic element
3
Force that attracts objects together
5
Reddish electrical conductor
6
Second lightest element
10
Curved glass that refracts light
11
Gas essential for breathing
12
Tissue that contracts for movement
Down
2
Molten rock beneath Earth surface
4
Magnetic metallic element
7
Blocking of light by a celestial body
8
Substance with pH above 7
9
Compound containing oxygen
13
The Red Planet