1. The Periodic Table of Elements

2. Periodic Table Originally arranged by increasing atomic mass
Arranged by Russian chemist Dimitri Mendeleev (late 1800’s)
Originally arranged
by increasing atomic
mass
Later arranged by
increasing atomic #
(Henry Moseley)

3. Columns Known as Groups or Families
A group or family has similar but not identical properties
Example: Group 1 or Alkali Metals
Properties – soft, white, shiny metals, highly reactive

4. We Are Family!

5. Periodic Table Organized into Rows = Periods
Columns = Groups or Families

6. Special Groups Group 1 – Alkali Metals Group 2 – Alkaline Earth Metals
Group 17 – Halogens
Group 18 – Noble Gases

7. Metals/Non-metals Notice the dark stairstep line.
Separates metals from nonmetals

8. Metals/Metalloids/Nonmetals
Properties between metals and nonmetals
Have a side touching the stairstep line EXCEPT Al (metal)
Nonmetals

9. Rows
Known as periods
Are not alike in properties, but there is a pattern
The first element in a period is almost always a reactive solid
The last element is an inert or inactive gas

10. Group Practice Calcium Tellurium Cesium Chlorine Argon
Give the group number for each element:
Calcium
Tellurium
Cesium
Chlorine
Argon

11. Rows Each period tells you how many energy levels each atom has
Each energy level can hold a certain number of electrons
Energy level electrons
Energy level electrons
Energy level electrons

12. Practice Give the element from the periodic table: Period 2, Group 14

13. Why do we care about how many electrons an atom has?
The reactivity of an element is due to its valence electrons
Valence electrons are the electrons found in the outer shell of an atom.
Shell or Energy Level
Nucleus
Valence Electrons

14. Trick to the Dot Diagrams
Some atoms are very easy to figure out how many electrons are in the valence shell
Group 1 has 1
Group 2 has 2
Group 13 has 3
Group 14 has 4 (are you noticing a pattern yet?)
Group 15 has 5
Group 16 has 6
Group 17 has 7
Group 18 has 8
Groups 3-12 always have 2 electrons

15. Dot Diagrams
A diagram to represent electrons in the outer energy level of an atom
Uses the atomic symbol and dots
Example: Hydrogen H•
Beryllium Be:
Carbon : C :

16. Dot Diagram How-To Figure out how many valence electrons the atom has.
Write the symbol for the element.
Add dots in pairs on each side of the symbol (imagine that it is inside a box) to represent the valence electrons.
Example:
Silicon
4 valence electrons

17. Dot Diagram Practice Draw Dot Diagrams for each of the following:
Hydrogen
Chlorine
Calcium
Nitrogen
Aluminum