Smells Unit – Investigation IV Polar Bears and Penguins

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

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

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

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

Classwork : Complete questions Classwork is due at: Unit 2 • Investigation IV

Making Sense What does electronegativity have to do with polarity? Unit 2 • Investigation IV

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

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

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.) Unit 2 • Investigation IV

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

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. Unit 2 • Investigation IV

Notes (cont.) Unit 2 • Investigation IV

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. Unit 2 • Investigation IV

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

(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