Across
- 2. Group 18 on the periodic table, least reactive
- 5. Positive charge in particles
- 7. Elements found to the left of the stair step line
- 9. Group 17 on the periodic table, most reactive gases
- 11. Metals founding the first group of the periodic table
- 12. Atoms with the same element, but different numbers of neutrons
- 13. Capital letter, With or without a lowercase accompanying it
- 17. Electrons on the outer ring of the element shell
- 19. The only gaseous element to the left of the stair step line
- 20. Neutral charge in particles
Down
- 1. Columns on the periodic table
- 3. The smallest part of an element
- 4. Elements found on the stair step line
- 6. Positively charged center of an atom
- 8. Negative charge in particles
- 10. Number of protons
- 14. The only metal not solid at room temperature
- 15. Rows on the periodic table
- 16. Elements found to the left of the periodic table
- 18. Number of protons + number of neutrons