1. Unit 3: Electrons Aim 3.2: How are electrons organized in atoms? Do Now: *Reference Tables Out *Silently complete the Do Now on the CW HW: *Last page of the CW *Test Corrections due Friday

2. Do Now: Complete the info for the Li-7 atom. Mass # = _______ Atomic # = ______ #P = ___________ #e- = __________ #N = __________ What is the total charge of the nucleus? _________ Why? What is the total charge of the Li- 7 atom? _______ Why?

3. 1.How are e-’s organized in an atom? Notes Electron Configuration: The number of e- ‘s in each electron shell (aka “energy level”) a) Write the e- configuration of Li: b) In the diagram, label the first electron shell as “1” and the second shell as “2” c) Where in the periodic table does it say the electron configuration of an atom?

4. When are atoms the most stable? (The Octet Rule) Notes Valence Shell: The outermost electron shell of an atom. The Octet Rule: Atoms want to fill their valence shell to become stable. The first shell holds two electrons, the other valence shells hold eight. Noble Gases: The elements in Group 18 which have a full valence shell and are inert (not chemically active). a) Label the valence shell in the Neon atom. b) How many valence e - ‘s does Neon have? _________

5. The Lewis Electron-Dot Diagram aka a Lewis Structure Notes Lewis Electron Dot Diagram (aka a Lewis Structure) – an element’s symbol surrounded by its valence electrons. a) How many total electrons does Li have? __________ b) How many valence electrons does Li have? ________ c) Draw a Lewis Electron Dot Diagram for an atom of the element Be.

6. 4. How can electrons move from one e - shell to another? Ground State Configuration – when all electrons of an atom are at their lowest possible energy level. This is shown in the reference tables. Excited State – if an electrons absorbs energy from the environment, it can jump to a higher electron shell/energy level. *The number of electrons, protons, and neutrons does not change.

7. 4. How can electrons move from one e - shell to another? a) What is the ground state electron configuration of an atom of Carbon? b) Which is a possible electron configuration for a Carbon atom with an excited electron? (1) 2-4 (2) 2-3 (3) 2-4-1 (4) 2-3-1 (c) Describe, in terms of electron shells, what happens when an electron absorbs energy and becomes “excited?”

8. Classwork: 20 minutes 1. What is the total number of valence electrons in…. (Strategy: Find the electron configuration in the periodic table) a) a Flourine (F) atom in the ground state. __________ b) a Magnesium (Mg) atom in the ground state. ________ c) a Neon (Ne) atom in the ground state. _________ d) a Sodium (Na) atom in the ground state. __________

9. Draw a Lewis Electron-Dot Diagram for an atom of each of the following elements: (Strategy: Find the number of valence electrons using the periodic table)

10. The atomic structure of N-14 Mass # = ___________ Atomic # = _________ #P = ___________ #e- = __________ #N = __________ What is the total charge of the nucleus? _________ Why? What is the total charge of the Li-7 atom? _______ Why? Draw N-14

11. N-14 Electron Configuration 1. Write the electron configuration of N-14 2. How many electron shells/energy levels does N-14 have? 3. How many valence electrons does N-14 have? 4. Which electron configuration could represent an atom of N-14 with an electron in the excited state? (a) 2-5 (b) 2-6 (c) 2-5-1 (d) 2-4-1 Draw a Lewis Structure for N-14

12. Lesson Wrap-Up 1.Where do you look to find the electron configuration of an atom? 2.What is the octet rule? (Use the word “valence shell” in your answer) 3.What information does a Lewis Structure show? 4.What is the difference between a ground state and excited state electron configuration?