Across
1
Second lightest element
2
Unit of heredity
6
Infectious microscopic agent
8
Compound containing oxygen
11
Unit of force
Down
2
Force that attracts objects together
3
Hottest planet in solar system
4
Icy body with a tail near the sun
5
Unit of energy
7
Substance with pH above 7
9
Positive particle in nucleus
10
Gas essential for breathing