1. Wednesday November 17, 2010 (Electron Dot Notation; Lewis Structures)

2. Which of the following elements would most likely share a pair of valence electrons with a chlorine atom in order to bond? sodiumcesiumcalciumcarbon sodium: 3.0 – 0.9 = 2.1ionic cesium: 3.0 – 0.7 = 2.3ionic calcium: 3.0 – 1.0 = 2.0ionic carbon: 3.0 – 2.5 = 0.5polar-covalent therefore, carbon, because covalent bonds share

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5. Electron-Dot Notation Thus far we have seen three different types of notation: isotopic notation electron configuration notation orbital notation 1s 2, 2s 2, 2p 2 _____ _____ _____ _____ _____ 1s 2s 2px 2py 2pz

6. Electron-Dot Notation Here’s a fourth type of notation: Electron-Dot Notation is an electron-configuration notation in which only the valence electrons of an atom are shown, indicated by dots placed around the element’s symbol. Lower energy level, inner - shell electrons are not shown.

7. Electron-Dot Notation Example: Carbon Carbon is in group 14 and has four valence electrons. 1s 2, 2s 2, 2p 2 Here’s carbon’s electron-dot notation: C 1.Start with the elemental symbol. 2.In your mind, divide the symbol into quadrants, like a tic-tac-toe grid. 3.Beginning in any quadrant put a dot to indicate a valence electron. 4.Continue in a clock-wise direction, putting one dot in each quadrant before any quadrant gets a second dot. 5.Stop when you have put in the number of dots that correspond to the number of valence electrons that element has. ¢ ¢ ¢ ¢

8. Electron-Dot Notation Example: Fluorine Fluorine is in group 17 and has seven valence electrons. 1s 2, 2s 2, 2p 5 Here’s fluorine’s electron-dot notation: F 1.Start with the elemental symbol. 2.In your mind, divide the symbol into quadrants, like a tic-tac-toe grid. 3.Beginning in any quadrant put a dot to indicate a valence electron. 4.Continue in a clock-wise direction, putting one dot in each quadrant before any quadrant gets a second dot. 5.Stop when you have put in the number of dots that correspond to the number of valence electrons that element has. ¢ ¢ ¢ ¢ ¢ ¢ ¢

9. Electron-Dot Notation

10. In compounds, a pair of dots between two symbols represents the shared pair of electrons. An unshared pair (lone pair) is a pair of electrons that is not involved in bonding and that belongs exclusively to one atom. The pair of dots representing a shared pair of electrons in a covalent bond is often replaced by a dash.

11. Lewis Structures Electron Dot Notation representations are termed Lewis Structures. Lewis Structures are formulas in which: – an element’s atomic symbol represents its nuclei and inner-shell electrons. – dot pairs or dashes between two atomic symbols represent valence electron pairs in covalent bonds. – dots adjacent to only one atomic symbol represent unshared valence electrons.

12. Lewis Structures Lewis structural formulas indicate the kind, number, arrangement and bonds but not the unshared pairs of the atoms in a molecule. F-F H-Cl A covalent bond produced by the sharing of one pair of electrons between two atoms is called a single bond.

13. Lewis Structures Example Draw the Lewis structure of iodomethene, CH 3 I The formula shows one carbon atom, one iodine atom, and three hydrogen atoms. Write the electron-dot notation for each type of atom in the molecule. Carbon is in Group 14 and has four valence electrons. Iodine is in Group 17 and has seven valence electrons. Hydrogen above Group 1 has one valence electron.

14. Worksheet Dot Notation and Lewis Structures