Explanation:
1. K (Potassium)
2. Te (Tellurium)
3. F (Flourine)
4. group 11, period 4
5. group 18, period 4
6. group 12, period 6
7. Cl
8. Pb
9. W
10. Sb
11. Na
12. period 6, group 11
13. period 5, group 11
14. period 2, group 16
15. Groups 13–16 of the periodic table contain one or more metalloids
16. Hydrogen
17. Helium
18. Calcium
19. Cobalt
20. Carbon