Across
- 4. negative-ion
- 5. alkaline-metals
- 8. metalloid
- 12. transition-metals
- 15. alkali-metals
- 17. radioactive-decay
- 18. actinides
- 19. protons
- 23. positive-ion
- 24. period
Down
- 1. isotope
- 2. nonmetal
- 3. noble-inert-gases
- 6. amu
- 7. electron-cloud
- 9. atomic-number
- 10. ion
- 11. lanthanides
- 13. neutrons
- 14. electrons
- 16. metal
- 17. radioactivity
- 20. nucleus
- 21. halogens
- 22. group