Periodic Table

3. each horizontal rowof elements on the periodic table
6. a Russian chemist, discovered a pattern to the elements in 1869
7. "happening at regular intervals"
8. unreactive nonmetals and are in Group 18 of the periodic table
10. British scientist, determined the number of protons in an atom
12. forms a wide variety of compounds
13. less reactive than alkali metals are
18. another commonly found member of Group 16, can be found as a yellow solid in nature
19. gas at room temperature, makes up about 80% of the air that you breathe
20. very reactive because their atoms need to gain only one electron to have a complete outer level

1. each vertical column of element on the periodic table
2. most abundant element in the universe, found in large amounts in stars
4. elements in Group 1 of the periodic table
5. states that the repeating chemical and physical properties of elements change periodically with the elements' atomic numbers
9. makes up about 20% of air, necessary for substances to burn
11. found to the left of the zigzag line on the periodic table
14. most common element from Group 13, most abundant metal in Earth's crust
15. found to the right of the zigzag line on the periodic table
16. elements of Group 3 - 12
17. called semimetals, elements that border the zigzag line on the perioidc table