2. Commonly Unclear information Why O 3 blocks UV better than other molecules. CFC and Ozone Correlation between Atoms and Ozone Problem Allotropes Isotopes – What are they and how to differentiate them Groups and Periods Core vs. Valence Electrons Charge of Atoms

3. Ozone and Atoms … Why? So what? Why should we discuss atomic structure? Answer: In order to understand the differences between oxygen and ozone AND in order to gain an understanding of How ozone filters out UV light … WE need to consider its Structure

4. Allotropes of Carbon DiamondGraphite Buckminster Fullerenes “Bucky-balls”

5. Isotopes Tritium & Deuterium are isotopes of Hydrogen Isotopes- Same number of Protons … differ in number of Neutrons 1 1 H - Hydrogen 2 1 H – Deuterium 3 1 H - Tritium

6. Your Turn Specify the number of protons and neutrons in the following isotopes Uranium-235 (AKA 235 92 U) Carbon-14 Iodine-131 Sulfur-36

7. Valence and Core electrons Alright, What is this about valence and core electrons?

8. Electrons 1 Proton 1 electron Add one proton Hydrogen 2 Protons And 2 neutrons to stabilize 2 electron Helium Add one proton 2 electrons 1 electron 3 Protons And 4 neutrons to stabilize Lithium

9. Your Turn Predict the number of neutrons, protons, total electrons, and valence electrons in: Ca Al As Te

10. Alright …. After this excursion into the atom, we get to our primary motivation for studying the atom … MOLECULAR STRUCTURE. Molecular structure is the result of ATOMS bonding to each other Remember - Molecular structure accounts for Properties of molecules. Think allotropes of carbon.

11. Covalent Bonding Bonding is the result of sharing of valence electron pairs!

12. Systematic Drawing of Lewis Structures Lewis structures show bonding and placement of electrons in molecules. 1. Sum Valence electrons for all atoms in the molecule 2. Draw the skeleton structure showing which atoms are bonded to each other. (Atom written first – generally center) 3. Complete the octet of all atoms surrounding the central atom 4. Place any left over electrons on the central atom 5. If the central atom has less than 8 electrons, complete the octet of the central atom by sharing additional pairs of electrons with the outer atoms.