1. Polar Bonds
Chemistry
Mr. Scott

2. So Let’s Review… Two types of bonds that we’ve discussed… 1. Covalent
2. Ionic

3. Electronegativity
The measure of the ability of an atom in a bond to attract electrons
Increases from left to right on the periodic table and from bottom to top

4. Covalent Bonds Occur between two nonmetals
Electronegativity of the two elements is very close
Electrons are shared equally

5. Ionic Bonds Occur between a metal and a nonmetal
Cation (positive ion) and the anion (negative ion) have electronegativities that are very far apart
Electrons are “stolen” by the anion

6. But not all sharing is equal…
What happens when two nonmetals have electronegativities that are somewhere in between?
The atom with the higher electronegativity will have
the electron more than the
atom with the lower
electronegativity.

7. And these bonds are called…
POLAR BONDS
Polar bonds have a slightly positive atom (lower electronegativity) and a slightly negative atom (higher electronegativity)
But they’re not quite ions!
This is called a dipole

8. Lower Probability Density
Higher Probability Density

9. Polar Molecules
If the entire molecule has a slightly positive end and a slightly negative end then we call it a polar molecule.
Ex: H2O, HCl

10. And that’s why water works!
The interaction of the dipoles is what actually holds water together!
The slight negatives (Oxygen) are attracted to the slight positives (Hydrogens)
These are called
hydrogen bonds

11. And oil separates because…
Nonpolar molecules don’t interact with the charges of the dipoles, therefore the water and nonpolar molecules separate.
And that’s how cell membranes work!

13. Quick Recap…
How are polar and nonpolar covalent compounds similar? How are they different?
What is a dipole?
What is a hydrogen bond?
Why don’t oil and water mix?