1. Mendeleev’s Role Chapter 4.2 Organization and discovery Organization and discovery

2. Periodic table history John Newlands 1800’s Law of octaves. 63 elements Law of octaves – elements group in 8’s because they repeated the Same number of valence electrons

3. ► Dmitri Mendeleev ► 2nd person to work on the Periodic table ► Notice that elements didn’t Go together – some react violently ► Arranged by atomic Mass

4. ► Henry Mosley ► group them by atomic number and they would have a better pattern/flow ► Physical and chemical properties are functions of the atomic #

5. ► Periodic law- elements with similar properties occur in a regular pattern - Elements are arranged by increasing atomic number - Certain properties reoccur - Predictions can be made

6. Organization of the PT ► Columns go up and down  They are called families or groups  There are 18 diff families

7. Organization of the PT ► Rows go from left to right  They are called periods  Different properties  Valence electron increase.  Oxidation number changes

8. Oxidation Number ► The oxidation number is the number of electrons that an element wants to gain or give up to become happy(Stable). Shells need 8 to be ► The oxidation number is the number of electrons that an element wants to gain or give up to become happy(Stable). Shells need 8 to be ► except 1 st shell (need 2)

9. Oxidation Number ► Families valence e- go from 1 to 8 ► Oxidation numbers go from +1,+2,+3,+/-4, -3,-2,-1

10. ► Atomic number Symbol ► Protons & ► electrons ► Element name ► Atomic Mass ( Protons + Neutrons) ( Protons + Neutrons) Amu= SI unit for atomic mass

11. Ions ► Ions gain/lose electrons to become happy and by using the oxidation number you can determine how many.

12. Isotopes are atoms that gain/lose neutrons and their mass changes. The mass on the periodic table is the average of all isotopes

13. Changing An Atom