"Atoms & Molecules": HTML5 Crossword

Across

5. 2 or more atoms bonded together (8)
7. one of the three states of matter (5)
9. this subatomic particle is outside the nucleus (8)
11. anything that has mass or volume (6)
12. the symbol "O" stands for this (6)
14. this orbits the nucleus (8)
16. the # of protons in an atom (12)
17. a proton has this charge (8)
19. a cloud that is used to hold electrons outside of the nucleus (7)
20. where you can find protons & neutrons (7)

Down

1. the symbol "He" stands for this (6)
2. the symbol "H" stands for this (8)
3. how many parts to an atom (5)
4. the amount of space that a substance or an object takes up (6)
6. meaning of atoms (10)
8. this subatomic particle has a neutral charge (7)
10. what science is the study of matter? (9)
13. chart that organizes all of the elements (13)
15. 2 atoms bonded together (8)
18. a measure of the amount of matter in a substance or object (4)