1. L EWIS D OT D IAGRAMS Electron Configuration for s and p orbitals Valence Electrons: form and function

2. L EWIS D OT Named for Gilbert Lewis after the publication of his ideas in 1916 These diagrams show the valence electrons for atoms. For covalently bonded molecules, and others. For molecules, the diagram shows the electron pairs Shared pairs used in bonding Unshared pairs that occupy orbitals and affect the shape of the molecule. Electron pairs are negative and repel each other.

3. L EWIS D OT T ABLE ( S AND P ORBITALS COMBINED ) s 1 s 2 p 1 p 2 p 3 p 4 p 5 p 6 Noble: complete shells

4. L EWIS D OT WITH L EVELS As electrons are added, they fill electron shells in an order determined by which configuration will give the lowest possible energy. The first shell (n=1) can have only 2 electrons, so that shell is filled in helium, the first noble gas. In the periodic table, the elements are placed in "periods" and arranged left to right in the order of filling of electrons in the outer shell. So hydrogen and helium complete the first period.

5. R ULES FOR L EWIS D OT D IAGRAMS - O CTETS Atoms are more stable in a configuration like one of a noble gas with 2 electrons like He or 8 electrons like Ne, Ar, Kr, Xe, or Rn. Determine the number of valence electrons: what group or family of the periodic table is it in? A. Add an electron for a negative charge; subtract an electron for a positive charge on any atoms with a charge or from the molecule if it has a charge. Divide the total number of electrons by 2 to find the number of pairs. Na has one valence e-. Chlorine has 7 electrons.

6. O CTET R ULES -B UILDING A MOLECULE Place the least electronegative atom in the center (atoms that are more likely to have a negative ion) Hydrogen is never the center atom First try, arrange the electron pairs (EP) until all are used. One pair between each atom Up to three more pairs on each outer atom (only 2 for H) Include the bonding pair in each outer atom count (O has 2 pairs and 2 bonding pairs in CO 2 ) Remaining pairs go on the central atom

7. D RAW L EWIS D OT FOR M ETHANE (C AND 4H) Carbon is in group 14 with 1s 2, 2s 2, 2p 4 electrons. How many valence electrons? 4 electrons in the outer shell. Hydrogen is in group 1 with 1s 1. It is never central. Put C in the middle. Put electron pairs between each pair of atoms. Consider 3D space.

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