1. Elements & the Periodic Table Organizing the Elements Chapter 3 Section 1

2. Objective Questions How was the Periodic Table developed? What information does the Periodic Table present? How are Valence Electrons related to the Periodic Table?

3. Atomic Mass The average mass of 1 atom of the element

4. Dmitri Mendeleev Noticed that patterns appear when the elements are arranged in order of decreasing mass –1869 –Russia

5. Periodic Table Periodic means… –A regular, repeated pattern Arranged by… –Periods Rows –Left to right –Families (Groups) Columns –Top to bottom

6. Inside an Atom Nucleus –Proton “+” charge –Neutron “0” charge Electrons –“-” charge Found outside the nucleus

7. Atomic Mass Unit (AMU) Protons = 1 Neutrons = 1 Electrons = 0

8. Atomic Number The # of protons in the nucleus of an atom H = 1 He = 2 Li = 3

9. Each Square Includes… Name Atomic number # of protons Chemical symbol 1-2 letters Atomic mass # of protons + neutrons

10. Valence Electrons Electrons in the outermost shell

11. Families (Groups) The elements in each group of the periodic table have the same number and arrangement of outer electrons