Atoms and Molecules

2. accelerator special machine that smashes atoms
4. the charge of a proton
6. An ionic bond forms when positively and negatively charged ions ___ each other
9. atoms have the same number of protons and ___
10. the negative subatomic particle that travels in an orbit around the nucleus of an atom
12. In a ___ atom, the outermost shell is completely closed or filled
15. substance formed as a result of a chemical change
16. a row on the periodic table of the elements (horizontal)
18. the charge of an electron
19. the table used to classify the elements
20. a column on the periodic table of the elements (vertical)

1. atoms joined together
3. what scientists think about atoms, based on repeated observations
5. the study of matter and how substances change
7. this reaction occurs when molecules combine to form a new substance
8. a substance that contains only one kind of atom
11. this reaction breaks a compound into two or more simpler compounds
13. the smallest recognizable piece of an element
14. an atom that has gained or lost electrons
17. The atomic ____ of an atom is based on the number of protons in the nucleus
18. the center of an atom, holds the protons and neutrons