Catalyst – February (72-46)/2, 2011WAY BACK WEDNESDAY! HW OUT!1. What is the mass of an atom that has 14

protons and 15 neutrons?2. The reaction of baking soda and vinegar

at 25 degrees Celsius produces gaseous carbon dioxide for 1 minute. Which of the following do you think will happen if you react baking soda and vinegar at 50 degrees Cesius?

a) Less gas will be producedb) Gas will be produced for more than 1 minutec) The reaction will have a strong odord) The reaction will not occur

Today’s Agenda

CatalystReview Naming and FormulasElectronegativity Difference, Bond Type, and Bond Polarity

Review = Time to WORKExit Question

Today’s Objectives

SWBAT name ionic and covalent compounds using CORRECT rules.

SWBAT determine bond type (ionic or covalent) using electronegativity differences (∆EN).

SWBAT get ready to DOMINATE both phases of the Unit 3 Test!

REVIEW OFNAMING &

FORMULAS!

Yo Yo! Let’s break it down!

IONICMetal + Nonmetal

Writing Formulas:Kriss Kross chargesNaming:2nd element ends in

–ide, ignore subscripts

COVALENTNonmetal + NonmetalWriting Formulas:Prefixes = subscript

#sNaming:Use prefixes, 2nd

element ends in -ide

How do we know if this is a covalent compound?

Is it between a metal and a non-metal? YES!!! Then, it is ionic!!!

Is it between a non-metal and a non-metal? YES!!! Then, it is covalent!

A compound made from Lithium and Oxygen

How do we know if it is ionic or covalent? Metals and non-metals make ionic compounds

Naming Ionic Compounds

Ionic Bond

Cation: Li Anion: O

Li O

Ionic Bond

Cation: Li Anion: O

Li+ O2-

Ionic Bond

Li+ O2-

Cation: Li Anion: O

Ionic Bond

Cation: Li Anion: O

Li2O

MgO

Naming Ionic CompoundsMgO

Magnesium Oxide

NBr3

Naming Covalent Compounds

NBr3

Nitrogen tribromide

Write the names and formulas…First! Decide if it’s ionic or covalent!

Write names

1. Na2O2. CO2

3. CaBr

4. Na2CO3

5. Mg3P2

6. K2S7. N2S3

Write formulas

1. Carbon monoxide2. Barium nitrate3. Xenon difluoride4. Carbon tetrachloride5. Sodium carbonate6. Lithium fluoride7. Nitrogen trifluoride

How to tell ionic and covalent apart We can look at the formula:

Ask yourself: Is it a metal and nonmetal or nonmetal and nonmetal?

Key Point #1: Along with looking at the formula, we can also look at electronegativity differences (∆EN) in to determine bond type (ionic or covalent).

Electronegativity Differences We can also look at electronegativity

differences (∆EN) Look at Electronegativity Chart to find

element electronegativities Find the difference by using subtraction Look at Bond Type Chart to determine bond

typesElectronegativity Chart

Remember…

Electronegativity is an atom’s ability to attract electrons to itself in a chemical bond

Electronegativity is expressed in numerical values of 4.0 or less These numerical values are called Paulings

Higher number means the atom will attract electrons more strongly

Electronegativity Chart

Pauling Values

Bond Polarity

Key Point #2: Bond polarity is based on differences in electronegativities of atoms forming a bond As electronegativity difference (∆EN) increases, polarity of bond increases

Bond Polarity Terms to KnowPure Ionic = Complete transfer of electrons from one atom to another

Polar Covalent = Unequal sharing of electrons between two atoms

Nonpolar Covalent = Equal sharing of electrons between two atoms

Pure Ionic Bonding Total give and take (transfer) of electrons!

= Big ∆EN!

I have no

chance!

Covalent Bonding is like a Tug-of-War

The more electronegative atom will pull electrons harder

Polarity and Electronegativity Polar Covalent -

electrons are pulled more toward one of the atoms

Big ∆EN!

Nonpolar Covalent - electrons are shared equally between atoms

Low ∆EN!

Big Dog – Little Dog

Medium Dog – Medium Dog

Polarity Ranges

Key Point #3: Bonds are not purely ionic (I) or purely covalent (NPC). They could be slightly ionic (VPC) or slightly covalent (MPC).

How to Calculate Electronegativity Difference (∆EN)1. Using Electronegativity Chart,

find Pauling values for each element

2. Subtract the smaller number from the bigger number

Example: 4.0 (F) – 0.9 (Na) = 3.1

3. Look at Bond Type Chart to determine bond polarity

Bond Type Chart – Copy into notes!

DEN Range Bond Type

0.0 – 0.39 Nonpolar Covalent

0.4 – 0.89 Moderately Polar Covalent

0.9 – 1.69 Very Polar Covalent

1.7 or greater Ionic

Example 1

Determine the type of bond in LiBr

1. Find electronegativity of each atom

Electronegativity Chart

Example 1

Determine the type of bond in LiBr

1. Find electronegativity of each atom

Li = 1.0 Paulings, Br = 3.0 Paulings

Example 1

Determine the type of bond in LiBr

1. Find electronegativity of each atomLi = 1.0 Paulings, Br = 3.0 Paulings

2. Find Electronegativity Difference (∆EN)DEN = 3.0 – 1.0 = 2.0

3. Look at chart to determine bond type.

Bond Type Chart

DEN Range Bond Type

0.0 – 0.3 Nonpolar Covalent

0.4 – 0.9 Moderately Polar Covalent

0.9 – 1.69 Very Polar Covalent

1.7 or greater Ionic

Example 2

Determine the type of bond in LiBr

1. Find electronegativity of each atomLi = 1.0 Paulings, Br = 3.0 Paulings

2. Find Electronegativity Difference (∆EN)DEN = 3.0 – 1.0 = 2.0

3. Look at chart to determine bond type.

Bond Type: Ionic

Example 2

Determine the type of bond in O2

1. Find electronegativity of each atom

Electronegativity Chart

Example 2

Determine the type of bond in O2

1. Find electronegativity of each atom

O = 3.4 Paulings, O = 3.4 Paulings

Example 2

Determine the type of bond in O2

1. Find electronegativity of each atomO = 3.4 Paulings, O = 3.4 Paulings

2. Find Electronegativity Difference (∆EN)DEN = 3.4 – 3.4 = 0

3. Look at chart to determine bond type.

Bond Type Chart

DEN Range Bond Type

0.0 – 0.3 Nonpolar Covalent

0.4 – 0.9 Moderately Polar Covalent

0.9 – 1.69 Very Polar Covalent

1.7 or greater Ionic

Example 2

Determine the type of bond in O2

1. Find electronegativity of each atomO = 3.4 Paulings, O = 3.4 Paulings

2. Find Electronegativity Difference (∆EN)DEN = 3.4 – 3.4 = 0

3. Look at chart to determine bond type.

Bond Type: Nonpolar Covalent

How Polar Is It?

Determine the polarity of each bond in the following compounds by calculating the electronegativity difference for each:

1. CO 4. HF2. AlP 5. CaO3. N2 6. H2

Electronegativity Chart

Bond Type Chart

Range Bond Type0.0 – 0.3 Nonpolar

Covalent0.4 – 0.9 Moderately

Polar Covalent0.9 – 1.69 Very Polar

Covalent1.7 or greater Ionic

Practice Time!

Please finish the worksheetThen, you can work on the Unit 3 Review Sheet

U3T Phase I Tomorrow!U3T Phase II on Friday!

Exit Question

Magnesium is a metal. Sulfur is a nonmetal.

What type of bond is formed between these elements?

Describe two ways that you could use to determine your answer to number 1.