Bellringer/Section 2 Notes. Notebook #5 (2-9-11) One way to organize a large group of objects is to arrange them into groups of similar objects. This is how scientists organize all of the many elements. Practice the skill of categorizing using the list of magazines below. Calling All Girls Homeopathic Medicine Modern Housekeeping Computer World Sports and Scores Easy Car Repairs Beautiful Homes Calling All Boys The Health Newsletter Auto Racing All About Computing Football Stories The Healthy Man Home Decorating Read Aloud Stories Sporting Times Classic Cars Building a Web Site Child’s Play The Healthy Woman Home Makers Magazine Family Computing Golf for Everyone The Sports Car Story Modern Homes Nursery Rhymes Good Nutrition Car Trends How to Use the Internet Tennis Tips Arrange the magazines into similar groups. What criteria did you use for grouping the magazines? Once you arrange the magazines into groups, could you sort the material further to make it even more organized?

I. Organization of the Periodic Table Periodic Law – Elements are arranged based on their characteristics This ensures the properties of elements follow a regular pattern B. Each vertical column is called a group OR family Elements in a group have similar properties. 2. They have similar properties because they have the same # of electrons in their outer energy level 3. We can represent the valence electrons by making an electron dot diagram – uses the symbol of the element & dots to represent the electrons in the outer energy level

Argon Ar F Fluorine

C. Periods – Horizontal rows. Number of energy levels II. Ions A charged atom is called an Ion Ions are formed when atoms gain or lose electrons 2. Ions may have a positive charge or a negative charge Positively charged ion – cation b. Negatively charged ion – anion

III. How Do The Structures Of Atoms Differ? Atomic Number – The number of protons in an atom Since atoms are neutral, the atomic number also gives the number of electrons B. Mass Number – The number of protons PLUS the number of neutrons C. Isotopes – Atoms that have a different number of neutrons

Practice/Review Draw Electron-dot diagrams for the following elements: Boron Sodium Lithium Phosphorus Helium

Example: Carbon Symbol: C Atomic Number: 6 # of valence electrons: 4 Mass Number: 12.01 # of energy levels: 2 # of Protons: 6 # of Electrons: 6 # of Neutrons: 6 Group: 14 Period: 2

Model: - Protons - Neutrons X X X - Electrons X X X X