1. Polarity of Molecules
301 Chemistry

2. Polar Bonds H—X The bond has partial ionic character
When the electronegativities of H and X are different,
the resulting bond is polar:
H—X
δ+ δ -
The bond has partial ionic character

3. Polarity is a continuum

4. Polarity is a continuum
Non-Polar Covalent – Bonds which occur between atoms with little or no electronegativity difference (less than 0.5).
Polar Covalent – Bonds which occur between atoms with a definite electronegativity difference (between 0.5 and 2.0).
Ionic – Bonds which occur between atoms with a large electronegativity difference (2.0 or greater), where electron transfer can occur.

5. Three Possible Types of Bonds
Pure covalent
Polar Covalent
Ionic

7. Dipole Moment
Dipole Moment occurs in any polar covalent bond, because of an unequal sharing of the electron pair between two atoms
Polar Molecules have permanent dipole moments

8. Net Dipole
In a molecule with two or more polar bonds, each bond has a dipole moment contribution = bond dipole
Net dipole moment = vector sum of its bond dipoles
Linear Molecules: CO2 is Non-polar
Because CO2 dipoles are orientated in opposite directions. Net dipole = 0
The dipoles have equal magnitudes and therefore they cancel

9. Shapes Symmetrical Unsymmetrical Linear Trigonal Planar Tetrahedral
Trigonal Bipyramid
Square Planar
Octahedral
Bent
Trigonal Pyramid
T-shaped
Seesaw
Square Pyramid

10. The shape of the molecule and Number of e- sets Are there polar bonds?
Are polar bonds arranged symmetrically?
Will polar bonds cancel each other?
Will there be a net dipole on the molecule? Cl C
The CCl4 molecule is a tetrahedral shape because the 4 bonding electron sets repel each other evenly
The CCl4 molecule has 4 polar C-Cl bonds
These 4 polar C-Cl bonds are arranged symmetrically in the CCl4 molecule
Because the 4 polar C-Cl bonds are arranged symmetrically in the CCl4 molecule they cancel each other and the CCl4 has no net dipole and is nonpolar

11. Are polar bonds arranged symmetrically?
The shape of the molecule
And number of e- clouds around central atom
Are there polar bonds?
Are polar bonds arranged symmetrically?
Will polar bonds cancel each other?
Will there be a net dipole on the molecule?
The NH3 molecule has 4 e- clouds (3 bonding and 1 non bonding) around the central N atom which repel each other into a trigonal pyramid shape x x N H H H
The NH3 molecule has 3 polar N-H bonds
These polar N-H bonds are arranged unsymmetrically in the NH3 molecule
Because the 3 polar N-H bonds are arranged unsymmetrically they do not cancel each other and the NH3 has an overall net dipole causing the NH3 to be polar