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POLARITY & VSEPR SHAPES

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POLARITY & VSEPR SHAPES

Ionic: exchange of e- btn 2 atoms

Covalent: equal sharing of e- btn 2 atoms

Polar Covalent: unequal sharing of e- btn 2 atoms

- Check difference in electronegativity btn the 2 atoms
- NOTE: noble gases have no # indicating a value of 0

∆EN Covalent 0 – 0.5

Polar Covalent 0.5 – 1.7

Ionic > 1.7

- If e- are not shared evenly btn 2 atoms, the atom with a stronger pull on e- (higher EN) becomes slightly –ve and the other atom becomes slightly +ve this is called a dipole and can be drawn in 2 ways

Gr. 11 Method:

ς-ς+

O – H

Gr. 12 Method:

O – H

- Check electronegativity difference 1st – if ionic or covalent the question of polarity is answered
- If polar covalent, VSEPR shape must be checked to determine if dipoles cancel

- Assuming all surrounding atoms are identical, the following is true about overall polarity of the following shapes:
Non-polar: dipoles cancel due to shape

- Parent shapes + square planar
Polar: dipoles do not cancel out due to shape

- Kid shapes except square planar

- Consider the following parent shapes:

- On Board
- NCl3
- SF4
- PO43-

- A shape which is normally non-polar can be made polar if the dipoles don’t cancel
- This will happen if the surrounding atoms are different, therefore having different sized dipoles

- On Board
- CH3Cl
- BCl2Br