横向
1
Substance with pH below 7
3
Compound containing oxygen
4
Naturally occurring inorganic solid
7
Particle of light
9
Path of a planet around the sun
11
Gas form of a liquid
12
Smallest unit of an element
纵向
2
Second lightest element
5
Our home planet
6
Preserved remains of ancient life
7
Positive particle in nucleus
8
Reddish electrical conductor
10
Unit of electric potential