Test 7: Chemical Bonding Cartoon courtesy of NearingZero.net

Basic Info (Put these notes on page 1 of your Bonding Packet) 1.Chemical bonds are attractive forces that hold atoms together. 2. Compounds – 2 or more different atoms chemically bonded together ex: NaCl or H 2 O 3. Diatomic Elements – 2 of the same atoms bonded together ex: H 2 O 2 F 2 Br 2 I 2 N 2 Cl 2

(Put on page 1 of packet) 4. Electronegativity – an atom’s attraction for electrons (Table S) Metals – Low #’s Nonmetals – Big #’s Think Metals lose e- & form + ions Nonmetals gain e- & form - ions

Electronegativity (attraction for another atom’s electrons) Hey! I find your electrons attractive! Get lost, loser!

Chart to Memorize! (page 1) Type of Bond IonicPolar Covalent Nonpolar Covalent Electronegativity Difference… >1.7 (equal to or more than 1.7) 1.7>x>0 (less than 1.7 but more than zero) = zero Valence Electrons are… TransferredShared unequally Shared Equally How to Recognize… Metal & Nonmetal 2 Different Nonmetals 2 of the same Nonmetals Chemical Formula for one example… NaClH2OH2OH2H2

Electronegativity Chart To Determine Electronegativity Difference for CaBr 2 : Br = 3.0 Ca = 1.3 Difference is 1.7 So CaBr 2 Bond is Ionic

Formation of Ionic Bond Note: Electrons are transferred

NaCl Crystal Lattice

The melting points of some Ionic Compounds are as follows: NaF 993 o C KCl 770 o C LiCl 605 o C These high melting points are experimental evidence that Ionic Bonds are VERY STRONG. (Hard to break just by heating).

Formation of Polar Covalent Bond Note: Electrons are shared

Animation for Bonds

Chemical Bonding (page 2) 1.Octet Rule – Atoms want to have 8 valence electrons (except H & He – need 2). 2.Forming Bonds – releases energy. Mg + S  MgS + energy (energy after  means its given off) 3.Breaking Bonds – requires energy. MgS + energy  Mg + S (energy before  means its needs or absorbed)

4. Ionic Bond – ED 1.7 or more 5. Polar Covalent Bond – ED greater than 0, but less than Nonpolar Covalent Bond – ED = zero 7. Table S – to calculate ED 8. Metallic Bonds – sea of mobile e- (this is a special type of bond that holds atoms of metals together & accounts for a metal’s luster and ability to conduct electricity)

Bond Wheel (page 3) E.D. Ionic 1.7 or more Polar Covalent less than 1.7 Nonpolar Covalent = zero

HW Do page 5 & 6

Nonpolar Molecules May have PC or NPC chemical bonds, but are Nonpolar Molecules due to their symmetry. Examples: H 2 O 2 F 2 etc. CH 4 CCl 4 CF 4 etc. CO 2

Polar Molecules Polar Molecules have PC bonds and are Asymmetrical. They have uneven e- distribution. They have a positive and negative end. Examples: H 2 O NH 3 HF HBr HCl CO

Intermolecular Forces Attraction between polar molecules Example

Hydrogen Bonding Extra strong IMF Found for H with NOF H 2 O NH 3 HF