Across
- 2. around the nucleus
- 3. metal+metal
- 4. non-metal+non-metal
- 5. the mass of an atom expressed in atomic mass units
- 8. created the Periodic Table
- 12. holds quarks together
- 13. metal+non-metal
- 14. tiny piece of everything
- 15. zero charged particle
- 17. in the middle of an atom
- 18. has the same number of protons
- 20. positively charged particle
Down
- 1. a unit of mass that describes the mass of an atom or molecule
- 6. makes up everything in the universe
- 7. number of protons of an atom
- 9. the sum of the numbers of protons and neutrons in the nucleus of an atom
- 10. negatively charged particle
- 11. the number of groups in the Periodic Table
- 16. an atom
- 19. a charged atom