Bond Polarity and Electronegativity

Unit 6 Lesson #6: Bond Polarity

You will need an electronegativity table and polarity range reference (remote students: see the daily folder; in-person students: pick up a copy of these)

This lesson's objectives:

• To calculate electronegativity (EN) differences

• To determine if a bond is polar or nonpolar

Get ready for the first review question...

Multiple Choice

REVIEW: do you recall what electronegativity (EN) is?

• the ability of an atom to attract electrons

• the ability for an atom to lose electrons

• the size of an atom's radius

• the molecular geometry of the structure

Electronegativity

• Recall: electronegativity is the ability of an atom to attract electrons

• It's based on the location on the periodic table

• REMEMBER: the top right-hand corner (excluding the noble gases) have the highest EN....WHY??

The next slide has a brief (~1.5 min) video describing EN and the 2 main factors affecting the trend

• Listen carefully...there will be a couple of questions afterwards

• Listen for why EN increases across the period

• Listen for why EN decreases down a group

Multiple Choice

What accounts for the increases in EN across a period (left to right)?

• the increase of protons in the same energy level

• the increase of electrons in the same energy level

• the decrease of protons in the same energy level

Multiple Choice

Why does the addition of protons result in?

• increased nuclear pull

• decreased nuclear pull

• increased ionization energy

• decreased ionization energy

Multiple Choice

Why does EN decrease as you move down the group (column)?

• addition of energy levels

• addition of electrons

• addition of nuclear pull

Polarity of Bonds

• Polarity depends on the difference between EN's of atoms in a bond

• The more EN difference, the greater bond polarity, If there is none (or little) EN difference, the bond polarity is nonpolar

Use the next 2 slides as references to determine bond polarity

• These images are also in the daily folder

Let's Practice Determining EN Difference and Bond Polarities...write your answers down

• Ex #1) H - Cl

• Locate the EN of H...

• Locate the EN of Cl...

• Find the difference between them

Ex #1 Continued...

*The EN of H is 2.1 and the EN of Cl is 3.0. Simply subtract...3.0-2.1 = 0.9

*Which range does this fall into? Pure covalent

Multiple Choice

The EN difference for

C - F is 1.5. Use your reference to determine the bond polarity.

• pure covalent

• polar covalent

• ionic

Multiple Choice

The EN difference for

C - H s 0.4. Use your reference to determine the bond polarity.

• pure covalent

• polar covalent

• ionic

Multiple Choice

The EN difference for

Na -F is 1.5. Use your reference to determine the bond polarity.

• pure covalent

• polar covalent

• ionic

Final Question...

Consider the illustration and jot down what you think. The final slide will ask you to share...

Open Ended

What do you think the ice cream represents? Which atom is represented by the polar bear? The penguin? What is this picture representing overall?