1. Daily science (pg. 50) Write the electron configuration for Bromine How many valence electrons does Br have? What is the Molar Mass of Br? Write the electron configuration for Li and Na. Notice any similarities? Write the electron configuration for Ne and Ar. Notice any similarites

2. PG. 53 The Periodic Table

3. History of the Periodic Table Dmitri Mendeleev was the first to organize the elements on the periodic table He arranged the elements in rows by increasing atomic mass Every time the chemical properties of an element repeated one he already had, he started a new row. Did this in 1869 He was able to predict new elements.  Ex germanium. Predicted it would be a gray metal with a high melting point

4. The current Periodic table Henry Moseley arranged the periodic table according to atomic number. Only a few elements changed places. The new table accounts for periodic law  Periodic law: arrangement of the periodic table so that elements that have similar properties appear at regular intervals.

5. Organization Group- a vertical column  Elements in the same column have very similar properties Period-a horizontal row  There are trends that increase and decrease down a row

6. Periodic Trends Valence electrons determine chemical properties There is an easy way to determine the number of valence electrons on the periodic table (see table for example)

7. Ion Formation Elements whose valence shells are not filled may undergo ionization If an atoms gains or loses electrons, it is no longer neutral and has a charge. It is then called an ion Each element wants a filled valence shell-or 8 electrons (this is called the octet rule) Can use the periodic table to predict which elements will form which ions (see table for example)

8. Classifying elements Elements are classified into 3 broad categories: metals, non-metals, and semi-conductors. Metals: Shiny solids. Can be stretched and shaped. Non-metals: Found on right side of table (except H). Can be solids, liquids, or gases. Poor conductors of heat and electricity (insulators) Semiconductors: 6 elements. Often called metalloids. Found in electronics.