1. Chemical Bonding ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

2. Why do atoms form bonds? To lower the chemical potential energy ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

3. What is a Chemical Bond? Chemical Bond – The force that holds two atoms together.  Electrostatic force between oppositely charged particles.  There are three types of bonds: Ionic Covalent Metallic $ What about polar covalent? ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

4. Ionic Occurs between metals and nonmetals Involves the transfer of electron(s) The metal donates electron(s) to the nonmetal This results in formation of: (+) Cation (-) Anion Picture made on WebMO ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

5. Electrostatic attraction between cation and anion create the ionic bond. An electron is transferred from a cation to an anion in an ionic bond. Ionic Bonding http://www.dorlingkindersley-uk.co.uk/static/clipart/uk/dk/sci_matter/image_sci_matter029.jpg ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

6. Lattice Structure ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

7. Covalent nonmetals Occurs between nonmetals sharing Involves the sharing of electron(s) Bond is overlap of electron clouds Two Types  Polar  Nonpolar ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

8. Polar Covalent Bond A covalent bond where the electrons are unequally shared. “Polar” means that the molecule has slightly positive and slightly negative poles. Caused by differences in electronegativities of elements that are bonded. H Cl Image from: http://images.google.com/imgres?imgurl=http://employees.csbsju.edu/hjakubowski/classes/ch123/HCl_H20ElDensity.gif&imgrefurl=http://employees.csbsju.edu/hjakubowski/classes/ch123/summer_chem/ch123OLSGMM0 405.htm&h=800&w=1000&sz=76&hl=en&start=23&um=1&tbnid=NpyhUO2LywGwRM:&tbnh=119&tbnw=149&prev=/images%3Fq%3Delectron%2Bdensity%2Bdiagrams%26start%3D20%26ndsp%3D20%26um%3D1%26 hl%3Den%26safe%3Dstrict%26rls%3DGWYG,GWYG:2007-21,GWYG:en%26sa%3DN ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

9. Polar Covalent Image from: http://www.800mainstreet.com/5/0005-008-negativity.htm ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

10. Nonpolar Covalent Bond The electrons are equally shared. There are no partial charges or attractions between the molecules. H H Image made using WebMO ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

11. Nonpolar Covalent Image from: http://www.800mainstreet.com/5/0005-008-negativity.htm ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

12. Quick Review Increasing Electronegativity Difference Bonding CovalentIonic Sharing Polar Sharing Nonpolar ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

13. Metallic Bonding Bonding between metals Electrostatic attraction between electrons and metal ions Electrons = delocalized  “Sea of electrons” ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

14. % Ionic Character Tells you if your compound will be ionic, polar covalent, or nonpolar covalent ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

15. Electronegativity Image from: http://www.800mainstreet.com/5/0005-008-negativity.htm ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

16. Determining % Ionic Character % Ionic Character tells you to what degree a bond is covalent or ionic. It can be determined by subtracting the electronegativities of the elements in the bond. Bonds with electronegativity differences between  0  0.2 are nonpolar covalent  0.2  1.7 are polar covalent  1.7  higher are ionic ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

17. Examples What type of bond exists between NO, N 2, NaCl, and CaO?  N-O = 3.44-3.04 = 0.40 = polar covalent  N-N = 3.04-3.04 = 0 = nonpolar covalent  Na-Cl = 3.16-0.93 = 2.23 = ionic  CaO = 3.44-1.00 = 2.44 = ionic ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

18. Properties of Ionic Compounds Crystalline solids (made of ions) chem.ps.uci.edu/~potma/COSMOS/Lectur e6.ppt ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

19. Properties of Ionic Compounds High melting and boiling points Image from Microsoft Office ClipArt ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

20. Properties of Ionic Compounds Conduct electricity when melted Image from Microsoft Office ClipArt ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

21. Properties of Ionic Compounds Conduct electricity when dissolved in water Pickle Video http://www.authorsden.com/ShortStoryImage/9551.gif ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

22. Properties of Ionic Compounds Many soluble in water but not in nonpolar liquids Animation Image from Microsoft Office ClipArt ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

23. Properties of Covalent Compounds Chlorine Gas Gases, liquids, or solids (made of molecules) Diamonds Water Images from Microsoft Office ClipArt ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

24. Properties of Covalent Compounds Low melting and boiling points Picture from: http://picasaweb.google.com/yogeshleo3107/SesonsGr eeting/photo#5111811977176549426 ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

25. Properties of Covalent Compounds Poor electrical conductors in all phases Picture from: http://picasaweb.google.com/yogeshleo3107/SesonsGreeting/photo#5111811977176549426 ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

26. Properties of Covalent Compounds Many soluble in nonpolar liquids but not in water ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

27. Properties of Metallic Compounds Strong Malleable Ductile Metallic Lustre Conductor of heat & electricity Images from Microsoft Office ClipArt ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright

28. Chemical Bonding Quiz ©2011 University of Illinois Board of Trustees http://islcs.ncsa.illinois.edu/copyright