Unit 4: Chemical Bonding PDF

UNIT 4: CHEMICAL BONDING  Bonding is a theoretical concept Based on indirect empirical evidence and logic  SCIENCE OF SLIME Problem: How does bonding affect the properties of a material? Follow procedure @ station to create slime Compare your slime with other groups...

UNIT 4: CHEMICAL BONDING  Bonding is a theoretical concept Based on indirect empirical evidence and logic  SCIENCE OF SLIME Problem: How does bonding affect the properties of a material? Follow procedure @ station to create slime Compare your slime with other groups What is going on?  Polymers Nylon, polyester Polyethylene, PVC  Why care about bonding theory? Explains structure  Why care about bonding theory? Explains physical & chemical properties Explains chemical reactions Breaking & formation of different bonds EXPLORATION – MOLECULAR MODELS =C =O =N = Cl =H Can you determine the formula? Name? How many types of connections (bonds) does each type of atom make? What kind of shape does it have? How would you draw it? BONDING THEORIES What is a bond? Electrostatic attraction between 2 particles Attraction for valence e- INTRAMOLECULAR BONDS Bonding within a molecule Bonding between atoms  HOW MANY BONDS? Only valence e- are involved in bonding Why? e- in lower energy levels are held strongly by the (+) nucleus Ex. Draw a Bohr diagram for Mg 1st energy level = 2 e- 2nd energy level = 8 e- 3rd energy level (valence) = 2e-  How many e- are in the valence energy level of each of the following? Na 1 P 5 Ca 2 O 6 Al 3 Cl 7 C 4 Ar 8  Orbital Region of space in which an e- is likely to be found 4 orbitals within the valence energy level  Each valence orbital may contain 0, 1 or 2 e- Max of 8 e- in valence Octet rule Within energy level, e- spread out to occupy empty orbitals BEFORE finding a buddy  Exception – H & He – only 1 valence orbital Maximum of 2e- LEWIS (ELECTRON DOT) SYMBOLS Way to show DISTRIBUTION of e- in valence orbitals Simplistic 2D diagram of complex 3D structures  How to draw: Atomic symbol (nucleus & inner energy C levels) Dots () = the valence e-; arrange around the symbol One dot must be placed in each of I the four orbitals before any pairing occurs 5th, 6th, 7th & 8th e- buddy up  LONE PAIR = pair of e- BONDING e- = single e- Could be shared or transferred I # bonding e- = # bonds  Bonding Capacity of Common Atoms Atom # of Valence e- # of Bonding e- Bonding Capacity Carbon 4 4 4 Nitrogen 5 3 3 Oxygen 6 2 2 Halogens 7 1 1 Hydrogen 1 1 1  Workbook Practice #1  BOND FORMATION When atoms collide, orbitals overlap Na Nucleus of each atom Cl attempts to capture the bonding e- of other atom Who wins?  Electronegativity Measure of an atom’s attraction for bonding e- Assigned value *Periodic Table* Metals Low Tend to lose e- Non-metals High Tend to attract e-  Rank the following 4 atoms from LEAST electronegative to MOST electronegative Al, Cl, Ca, Ar  Ca, Al, Ar, Cl Where would F- fit the in lineup? Why?  F-, Ca, Al, Ar, Cl F- has already gained an electron & has a full octet!  Difference in electronegativities determines the nature of the bond  1) COVALENT bond Molecular compounds High/similar electronegativities SHARE bonding pair 2 ways to share…  A) Non-polar Electronegativities are equal e- shared equally B) Polar Difference in electronegativities