1. Decoding the Periodic Table Part 2
CHAPTER 12
Decoding the Periodic Table Part 2

2. First Periodic Table
The first periodic table was devised by Dmitri Mendeleev and published in 1869, with 63 elements

3. Periodic Table —118 elements

4. Organization of the Periodic Table
18 columns (groups or families)
7 horizontal rows (periods)

5. Three Classes of Elements
Metals
(gold)
Nonmetals
(sulfur)
Metalloids (germanium)

6. Three Classes of Elements

7. Moving from left to right
As you move from left to right across a row, the elements become less metallic!

8. Groups
Elements in the same group have often have similar chemical and physical properties (also called “family”)

9. Grouping the Elements
Elements in a group have similar properties because they have the same number of electrons in the outer level (valence electrons)
Atoms give/take/share electrons with other atoms to have a complete set of electrons in their outer level
Elements that undergo such processes are called reactive and can combine to form compounds

10. Hydrogen Very reactive
Located above group 1 because it also has 1 electron in the outer level
Hydrogen’s physical properties are more like those of non-metals
The most abundant element in the universe

11. Group 1: Alkaline Metals
Very reactive
1 electron in outer level
Softness, color of silver, shiny, low density

12. Group 2: Alkaline Earth Metals
Very reactive, but less so than group 1
2 electrons in the outer level
Color of silver, higher densities than alkali metals

13. Groups 3-12: Transition Metals
Less reactive than alkaline earth metals
1 or 2 electrons in the outer level
Good conductors, shiny, higher densities and melting points than groups 1 and 2

14. Groups 13-16
Named for the first element in the group (i.e. boron, carbon…)
3, 4, 5 and 6 electrons in the outer shell respectively
Reactivity varies, but tend to be reactive

15. Group 17: Halogens Very reactive 7 electrons in the outer level
Non-metals
When halogens combine with metals they form salts

16. Group 18: Noble Gases Unreactive (very stable)
8 electrons in the outer level (with the exception of helium which has 2)
Colorless, odorless gases at room temp