chapter 8 shape of molecules. vsepr- stands for: valence-shell electron pair repulsion theory....
TRANSCRIPT
Chapter 8
Shape of molecules
VSEPR-
• Stands for: Valence-shell electron pair repulsion theory.
• States that pairs of valence e- arrange as far apart as possible.
Ball-and-stick models-
• 3D physical model – ball = atom– Sticks/spring = single bonds– curved springs/more then one spring =
multiple bonds.
Bond angle-
• The geometric angle between 2 adjacent bonds in a molecule.
Drawing 3D
• Single
• Double
• Triple
• Lone Pairs
CH4
Common Shapes: – Linear -atoms connect in a straight line.
– Lewis Dot Diagram:
Common Shapes:
– Bent molecules have a lone pair • Involves O or S
• Lewis Dot Diagram: 104.5°
Common Shapes:
– Trigonal planar- triangular and flat shape.• Involves B or Al
– Lewis Dot Diagram:
Common Shapes:
– Tetrahedral –3 sided pyramid w/ four surfaces.
• Involves C or Si
– Lewis Dot Diagram:
Common Shapes:
– Pyramidal -central atom bonded to 3 other atoms and has an unshared pair of valence e-
• Involves N or P
– Lewis Dot Diagram:107.5°
All geometries in book w/ names and angles – section 8-1
LinearTetrahedral
Trigonal planar
Pyramidal
Bent
104.5°
107.5°
Bond length-
• Down a group bonds lengthen
• Multiple bonds (double/triple) are shorter than single.
Skagen’s Homepage Chemistry Resources 1st slide
Chapter 8
Shape of molecules
8-2 PolarityDipole-
• One side of a molecule has a negative charge and the other side has a positive charge
Polarity-
• Is determined by the shape of a molecule and polarity of its bonds
Polar
Non-polar
Determining Polarity
Polar
• Non symmetrical
• Pyramidal and Bent are always polar - other shapes can be as well
• Symmetrical
• Linear, trigonal planer, and tetrahedral are possible non polar molecules
Non-Polar
Non-symmetric, Polar
Symmetric, Non-polar
If the molecule is:If the molecule is:
CovalentCovalent
The bonds are polar. If the shape is
The bonds are polar. If the shape is
Non-symmetricNon-symmetricSymmetricSymmetric
The molecule is polarThe molecule is polarThe molecule is non-polar
The molecule is non-polar
The molecule is non-polar
The molecule is non-polar
Ionic or two of the same element
Ionic or two of the same element