Across
- 1. contains the protons and neutrons
- 5. arranged by increasing atomic number and by changes in physical and chemical properties
- 8. the number of protons in the element
- 9. vertical columns in the periodic table
- 10. even smaller particles
- 12. negative 1 charge
- 13. the same element that have different numbers of neutrons
- 14. the smallest piece of matter
- 15. sum of the protons and the neutrons
Down
- 2. where electrons hang around the nucleus
- 3. positive 1 charge
- 4. 0 charge
- 6. represent the electrons in the outer energy level
- 7. weighted-average mass
- 11. horizontal rows in the periodic table