1. Introduction to Chemical Bonding

2. Chemical Reactions: During chemical reactions, elements combine, rearrange, or break apart with others to form new substances. New substances are created when chemical bonds are broken or created. http://www.polmag.pl/en/media/magnesium.jpg Magnesium Metal http://www.bcscience.com/images/m agnesium_burn.jpg Chemical Reaction Magnesium Oxide Original Substance New Substance http://jchemed.chem.wisc.edu/JCESOFT/CCA/CCA 3/STILLS/MAGAIR/MAGAIR/64JPG48/6.JPG

3. http://en.wikipedia.org/wiki/Self-heating_can Evidence of Chemical Reactions: Fire/Burning Color change without dye New gas created Heat released Heat absorbed http://amazingrust.com/Experiments /background_knowledge/Images/Fir e-big.jpg http://z.about.com/d/chemistry/1 /G/5/a/demonstration.jpg http://www.uncp.edu/home/mcclurem/pta ble/ca_2.jpg http://static.howstuffworks.com/gif/cold- pack.jpg

4. Compounds are more than one kind of element joined together. Octet Rule: Describes how chemical bonds happen. Atoms want a full valence (or outer electron energy level). Full valence will mean having 8 valence electrons. http://www.chemprofessor.com/periodicqm_files/image005.gif

5. Octet Rule … To reach full valence, some atoms “want” to lose electrons and others “want” to gain electrons. –Atoms with FEWER than 4 valence electrons will bond by losing those electrons. These atoms will become positively charged! –Atoms with MORE than 4 valence electrons will bond by gaining electrons (up to eight). These atoms will become negatively charged! –Atoms with 4 valence electrons can gain or lose electrons. It depends on the element to which it is bonding. It is easier for the atom to lose 1, 2 or 3 electrons rather than gaining 5, 6 or 7. Why are these atoms positive? Losing electrons (and electrons are negative) means more protons (positive charge) than negative charges. It is easier for the atom to gain 1, 2 or 3 electrons rather than losing 5, 6 or 7. Why are these atoms negative? Gaining electrons (and electrons are negative) means more negative charge than positive charges (protons).

6. A chemical bond is created by the sharing or exchange of electrons between elements. Example: Sodium (Na) Valence? 1 Easiest way to follow Octet Rule? Lose 1 electron If following Octet Rule, what’s the charge? +1 http://www.historyforkids.org/scienceforkids/chemistry/atoms/ pictures/sodium.jpg

7. Example: Fluorine (F) Valence? 7 Easiest way to follow Octet Rule? Gain 1 electron If following the Octet Rule, what’s the charge? –1 http:// www.bbc.co.uk/schools/gcsebitesi ze/science/images/diag_fluorine.gif

8. What will happen if Sodium and Fluorine atoms are mixed? Electrons could transfer between the atoms. A sodium atom could lose an electron to a fluorine atom. Both atoms are left with full valence & are bonded together, creating a compound.