"Atoms & Molecules": HTML5 Crossword

Across

2. one of the three states of matter (5)
4. where you can find protons & neutrons (7)
7. this subatomic particle has a neutral charge (7)
10. chart that organizes all of the elements (13)
13. the amount of space that a substance or an object takes up (6)
14. the symbol "H" stands for this (8)
16. 2 atoms bonded together (8)
18. anything that has mass or volume (6)
19. 2 or more atoms bonded together (8)
20. what science is the study of matter? (9)

Down

1. how many parts to an atom (5)
3. the symbol "O" stands for this (6)
5. meaning of atoms (10)
6. a proton has this charge (8)
8. this orbits the nucleus (8)
9. this subatomic particle is outside the nucleus (8)
11. the # of protons in an atom (12)
12. the symbol "He" stands for this (6)
15. a cloud that is used to hold electrons outside of the nucleus (7)
17. a measure of the amount of matter in a substance or object (4)