1. Smells Unit – Investigation IV
Polar Bears and Penguins

2. Admit Slip (cont.) Consider the following illustration:
Draw the Lewis dot structure for HCl.
If the penguin represents a hydrogen atom and the polar bear represents a chlorine atom, what does the ice cream represent in the drawing? What do you think the picture is trying to illustrate?
(cont.)
Unit 2 • Investigation IV

3. Agenda Admit Slip Comic Book Questions Notes Exit Slip
Product: Questions, Notes, Exit Slip
Homework: Draw picture
Unit 2 • Investigation IV

4. You will be able to: Recognize and explain a polar bond.
Unit 2 • Investigation IV

5. Activity
Purpose: In this lesson you will be exploring polarity and bonding between atoms in greater detail. A comic book will provide new information about these topics and will introduce you to the concept of electronegativity, which helps us to understand partial charges.
Unit 2 • Investigation IV

6. Classwork : Complete questions
Classwork is due at:
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7. Making Sense What does electronegativity have to do with polarity?
Unit 2 • Investigation IV

8. Electronegativity/Polarity 1/4/11
The tendency of an atom to attract electrons shared between two atoms is called electronegativity.
The most electronegative atoms are in the top right of the periodic table. The least electronegative are in the bottom left.
An atom that strongly attracts the shared electrons is considered highly electronegative and ends up with a partial negative charge on it.
The atom with lower electronegativity will end up with a partial positive charge on it. .
Unit 2 • Investigation IV

9. In a nonpolar covalent bond, the atoms have equal electronegativity and share electrons equally.
If the electronegativities between two atoms are even slightly different, they form what is called a polar covalent bond. They atoms share electrons unequally.
When the electronegativities between two atoms are greatly different, they form an ionic bond. In an ionic bond, one atom (a metal) completely gives it’s electron(s) to the other atom (a nonmetal).
Unit 2 • Investigation IV

10. A molecule can have polar bonds but not be a polar molecule overall.
The word dipole (which means two poles) is used to describe a polar bond or a polar molecule.
A molecule is polar if the ends of the molecule have two different charges.
A molecule can have polar bonds but not be a polar molecule overall.
(cont.)
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11. Notes (cont.)   This picture shows how to illustrate a polar bond.
The crossed end of the arrow indicates the positive (+) end of the polar bond and the arrow points in the direction of the negative (-) end
Unit 2 • Investigation IV

12. You also add the Greek symbols to show these charges. 
The more electronegative atom has the partial negative charge. The less electronegative atom has the partial positive charge.
You also add the Greek symbols to show these charges.
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13. Notes (cont.)
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14. Exit Slip
Is the bond between these atoms polar? Explain your reasoning.
How would the atoms be portrayed in the comic book—as polar bears, penguins, or both? Explain.
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15. Wrap-Up
Anytime there are two different types of atoms sharing electrons, there will be a partial negative charge on one atom and a partial positive charge on the other atom.
Electronegativity measures the tendency of an atom to attract the electrons in a bond.
(cont.)
Unit 2 • Investigation IV

16. (cont.)
The bonds are labeled nonpolar covalent, polar covalent, and ionic as the difference in electronegativity between the two atoms in the bond increases.
Unit 2 • Investigation IV