WARM UP Draw lewis structures for the compounds

WARM UP Draw lewis structures for the compounds below: 1) CF 4 2) BF 3 3) CO 2

VSEPR THEORY THE 3 D SHAPES OF MOLECULES

VSEPR THEORY • Valence Shell Electron Pair Repulsion • Predicts the 3 D geometry of molecules • The structure of covalent bonds around an atom is determined by minimizing electron-pair repulsions • Get electrons as far apart as possible! • Base structure depends on how many electron domains there are in the molecule • Molecule geometry depends on how many bonding pairs there are

BOND LENGTHS • Bond length increases as atomic radius increases • Bond length decreases with multiple bonds: • Single > Double > Triple • Remember: Bond strength increases as bond length decreases

TURN TO BACK OF YOUR NOTES We will finish the front in a little bit!

4 ELECTRON DOMAINS CF 4 NCl 3 H 2 Se

3 ELECTRON DOMAINS BF 3 NOH

2 ELECTRON DOMAINS C 2 H 2 • All diatomic compounds are linear • Most compounds with double or triple bonds are linear

BOND ANGLES Shape Angle of Bond Tetrahedral (4 e- regions) 109. 5° CF 4 Trigonal Pyramidal (4 eregions) Bent (4 e- regions) <109. 5° NCl 3 <109. 5° H 2 Se Trigonal Planar(3 e- regions) 120° BF 3 Linear (2 e- regions) 180° NOH

BOND POLARITY • Some molecules that have polar bonds are nonpolar! • If the dipole arrows cancel each other out, then the molecule does not have an overall dipole and will be nonpolar. • Examples: CO 2, BF 3, CF 4

WARM-UP Draw the Lewis dot structures (see your notes) WITH dipole arrows for the following 3 molecules. 1) Carbon Dioxide 2) Boron Trifluoride 3) Carbon Tetrafluoride