1. Chapter 5: The Periodic Table PEPS Rainier Jr/Sr High School Mr. Taylor

2. Section 1: Organizing the Elements  Russian chemist Dmitri Mendeleev in the 1860’s knew about 60 elements and their atomic masses.  When he placed these elements in order by atomic mass he saw that chemical properties repeated at regular intervals (periodic repetition).

3. Section 1: Organizing the Elements  Mendeleev’s table had gaps in it but he predicted the properties of these “gap” elements  Predictions were close when these elements were discovered.

4. Section 1: Organizing the Elements  A few elements did not fit the pattern  Henry Moseley (English chemist) rearranged the elements by atomic number; problem solved.  The Periodic Law : when arranged by increasing atomic number, elements have similar chemical properties that repeat at regular intervals (periods).

5. Section 1: Organizing the Elements Chemical symbol Chemical name

6. Section 1: Organizing the Elements  The rows are called periods  Elements become less metallic from left to right  The columns are called groups.  Each column (group) has similar chemical properties

7. Section 2: Exploring the Periodic Table  The periodic repetition of chemical properties is the result of the arrangement of electrons in the outer energy level (valence electrons).  Variations in physical properties are due to different atomic numbers (protons).

8. Section 2: Exploring the Periodic Table  Elements are place in;  Rows by the number of electron energy levels  Columns by the number of electrons in the outer energy level (valence electrons).

9. Section 2: Exploring the Periodic Table  Ion Formation  Atoms may gain or lose electrons to form ions  Ions are charged particles because they do not have the same number of protons and electrons (unbalanced charges).

10. Section 2: Exploring the Periodic Table  Ion Formation  Atoms gain or lose electrons to achieve a full outer energy level.  Group 1; loses an electron easily, has a positive charge (cation).  Group 17; gain an electron easily, has a negative charge (anion)

11. Section 2: Exploring the Periodic Table  Metals vs non-metals  Metals are  Shiny solids (mostly)  Malleable (able to be hammered into shapes)  Ductile (can be stretched into wires)  Conductors of electricity and heat

12. Section 2: Exploring the Periodic Table  Metals vs non-metals  Non-metals are  Solids, liquids, or gases at room temp.  Often dull and brittle  Poor conductors of heat and electricity (insulators)

13. Section 2: Exploring the Periodic Table  Metals vs non-metals  Semiconductors  Have some properties of metals and non-metals  Are used in computer chips

14. Section 3: Families of Elements  Elements of a family have the same number of valence electrons  Metals: left side of table  Non-metals: right side of table

15. Section 3: Families of Elements  Alkali metals: Group 1  One valence electron  Form an ion with a 1+ charge  HIGHLY reactive  Never found in Nature except combined with another element in a compound

16. Section 3: Families of Elements  Alkaline Earth metals: Group 2  2 valence electrons  Form a 2+ ion  Very reactive, but less than Group 1

17. Section 3: Families of Elements  Transition Metals  Number of valence electrons varies  Some are reactive (iron), some are not (Gold)  Many metals we use everyday are in this group (Iron, gold, aluminum, copper).

18. Section 3: Families of Elements  Noble gases: Group 18  Full outer valence electron energy level  Non-reactive gases do not usually form compounds or molecules.

19. Section 3: Families of Elements  Halogens: Group 17  7 electrons in outer energy level (almost full).  Gain 1 electron easily to fill the level; 1- charge  VERY reactive; combine easily with metals to form a salt (NaCl, KCl, SnF 2 ).

20. Section 3: Families of Elements  Other non-metals  Oxygen and Nitrogen are the most abundant gases in the atmosphere.  Carbon compounds form the basis of most of the molecules in living organisms.

21. Section 3: Families of Elements  Semiconductors  Also called metalloids  Silicon makes up 28% of the matter in the Earth’s crust  Sand is mostly silicon dioxide.