1. Valence Electrons I. Def- Electrons that are found in the outermost energy level or orbital. A. These are the electrons that are involved in chemical bonding and help atoms achieve stability. I. Determining the # of Valence Electrons A. S & P Block (main block elements)- 1. Group 1- 1 valence electron 2. Group 2- 2 valence electrons

2. 3. Group 13- take group #- 10= 3 valence electrons 4. Group 14- take group #-10= 4 valence electrons 5. Group 15, 16, 17, 18, etc. III. ALL ATOMS WANT TO HAVE 8 VALENCE ELECTRONS!!! A. Octet Rule- states that all atoms strive to have 8 valence electrons in their outermost energy level in order to achieve a stable arrangement. Ex. How many v. electrons does Calcium have? What element would it bond with to achieve stability?

3. The Periodic Table I. 3 main groups A. Metals- found on the left of the staircase 1. Good conductors of heat and electricity B. Non-metals- found on the right of the staircase 1. Poor conductors of heat and electricity C. Metalloids- found along the staircase 1. Possess properties of BOTH metals and non- metals.

4. II. Specific Group Names A. Group 1- Alkali Metals 1. MOST reactive group of metals. (due to having only 1 valence electron). B. Group 2- Alkaline Earth Metals C. Groups 3-12- Transition Elements D. Group 17- Halogens 1. MOST reactive group of non-metals (due to having 7 valence electrons) E. Group 18- Noble Gases 1. Most stable group on the periodic table (due to already full octet )

5. Average Atomic Mass of an Element 1. If percentages are given, convert to decimals. 2. Multiply the decimals by the mass of the isotope. 3. Add the masses together to get the average atomic mass for each element. Ex. 1.