Science Brain Teaser

Public|
8
2
4
5
1
7
3
6
9

Across

1

Ball of burning gas in space

3

Center of an atom or cell

6

Unit of energy

7

Smallest unit of an element

Down

2

Particle of light

4

Naturally occurring inorganic solid

5

The Red Planet

8

Nerve cell in the brain

9

Biological catalyst