1. Aim: What are polar bonds and polar molecules?

2. Polar and Nonpolar Bonds
There are two types of covalent bonds
Nonpolar Covalent Bonds (equal share of electrons)
Polar Covalent Bonds (unequal share of electrons)

3. Polar Covalent Bond
A Polar Covalent Bond is unequal sharing of electrons between two atoms (H-Cl)
In a polar covalent bond, one atom typically has a negative charge, and the other atom has a positive charge

4. Nonpolar Covalent Bond
A Nonpolar Covalent Bond is an equal sharing of electrons between two atoms (Cl-Cl, N-N, O-O)

7. Dipole When there is unequal sharing of electrons a dipole exists
Dipole is a molecule that has two poles or regions with opposite charges
A dipole is represented by a dipole arrow pointing towards the more negative end

9. Water is polar
A polar molecule is water soluble. In order for a solution to form with molecules, they must be either both polar or both non-polar.

10. solutions
water is a polar molecule - so is alcohol. When you mix water and alcohol you see a solution with both molecules in the solution. The molecules mix together. When you try to mix a polar and a non polar molecule what happens? They don't mix. water (a polar molecule) does not mix with oil (a non polar molecule).

11. Electronegativity
is defined as the ability of an atom in a particular molecule to attract electrons to itself
(the greater the value, the greater the attractiveness for electrons)

12. Electronegativity is a function of:
the atom's ionization energy (how strongly the atom holds on to its own electrons)
the atom's electron affinity (how strongly the atom attracts other electrons)

13. An element with high electronegativity:
Attract electrons from other atoms
Resist having its own electrons attracted away
Fluorine is the most electronegative element (electronegativity = 4.0)
the least electronegative is Cesium
(notice that are at diagonal corners of
the periodic chart)

14. General trends:
Electronegativity increases from left to right along a period
For the representative elements (s and p block) the electronegativity decreases as you go down a group
The transition metal group is not as predictable as far as electronegativity

15. Predicting the type of bond based upon electronegativity differences:
if the electronegativity difference is 0, the bond is non-polar covalent
If the difference in electronegativities is between 0 - 2, the bond is polar covalent
If the difference in electronegativities is
2.0 or more, the bond is ionic

16. Water is polar because:
of the differences in the electronegativity between oxygen and hydrogen.
Oxygen is to the right on the periodic table,
so Oxygen is highly negative compared
to hydrogen.

17. Water Molecule Structure
The oxygen attracts negative charges making the area around the oxygen much more negative than the area around the hydrogen.
The hydrogen area (positive charges) makes the molecule bend so that the 2 hydrogen atoms in the water are on the same side, pointing away from the negative area around the oxygen.

19. Polar or nonpolar? F2
the electrons are shared equally between the atoms, the bond is nonpolar covalent HF
fluorine has greater electronegativity than the hydrogen atom.
fluorine attracts electrons away from the hydrogen
The bond is a polar covalent bond

20. Properties of water due to its polarity:

21. Properties of water due to its polarity:
Hydrogen bonds
Cohesion
Adhesion
Capillarity
Universal solvent

22. Summary
In a polar bond, one atom is more electronegative than the other.
In a nonpolar bond, both atoms have similar electronegativities.
An asymmetric molecule with polar bonds is a polar molecule.
An asymmetric molecule with nonpolar bonds is a nonpolar molecule.
A symmetric molecule, regardless of the polarity of the bonds, is always a nonpolar molecule.