Across
- 2. the number of protons in the nucleus of an atom
- 3. vertical columns on periodic table
- 5. matter that is composed of only one type of atom
- 7. isotopes have different numbers of...
- 8. protons + neutrons
Down
- 1. horizontal rows on periodic table
- 4. subatomic particle with a postive charge
- 6. elements located on the left of the periodic table