Across
- 3. Noble gas used in balloons
- 5. Element in Group 7
- 6. Element with atomic number 12
- 7. Russian scientist who created the periodic table
- 9. Vertical columns in the periodic table
Down
- 1. Atoms of the same element with different neutron numbers
- 2. Group 1 metals
- 4. Total number of protons and neutrons
- 8. Subatomic particle with a negative charge