1. The Periodic Table of Elements

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

3. Columns Known as Groups or Families Known as Groups or Families A group or family has similar but not identical properties A group or family has similar but not identical properties Example: Group 1 or Alkali Metals Example: Group 1 or Alkali Metals Properties – soft, white, shiny metals, highly reactive 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 1 – Alkali Metals Group 2 – Alkaline Earth Metals Group 2 – Alkaline Earth Metals Group 17 – Halogens Group 17 – Halogens Group 18 – Noble Gases Group 18 – Noble Gases

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

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

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

10. Group Practice 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 period tells you how many energy levels each atom has Each energy level can hold a certain number of electrons Each energy level can hold a certain number of electrons Energy level 1 - 2 electrons Energy level 1 - 2 electrons Energy level 2 - 10 electrons Energy level 2 - 10 electrons Energy level 3 - 18 electrons Energy level 3 - 18 electrons

12. Practice Give the element from the periodic table: Period 2, Group 14 Period 4, Group 3 Period 3, Group 17 Period 1, Group 8 Period 4, Group 2 Period 2, Group 4

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

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

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

16. Dot Diagram How-To 1. 1. Figure out how many valence electrons the atom has. 2. 2. Write the symbol for the element. 3. 3. 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