1. Define periods and groups on the periodic table.
2. What group is iron in?
3. What period is gold in?
4. What element is period 4 group 16.
5. Find 20 elements and list their: Name, Date of discovery, and who discovered them.
6. What element is #56?
7. What element has the symbol Se?
8. What is the number and symbol for iron?
9. Who invented the periodic table?
10. When was the periodic table invented?
11. What are triads?
12. What are isotopes?
