Catalyst – February (72-46)/2, 2011 WAY BACK WEDNESDAY! HW OUT! What is the mass of an atom that has 14 protons and 15 neutrons? 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 produced b) Gas will be produced for more than 1 minute c) The reaction will have a strong odor d) The reaction will not occur

Today’s Agenda Catalyst Review Naming and Formulas Electronegativity Difference, Bond Type, and Bond Polarity Review = Time to WORK Exit 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 OF NAMING & FORMULAS!

Yo Yo! Let’s break it down! IONIC Metal + Nonmetal Writing Formulas: Kriss Kross charges Naming: 2nd element ends in – ide, ignore subscripts COVALENT Nonmetal + Nonmetal Writing Formulas: Prefixes = subscript #s Naming: 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!

Naming Ionic Compounds A compound made from Lithium and Oxygen How do we know if it is ionic or covalent? Metals and non-metals make ionic compounds

Ionic Bond Cation: Li Anion: O Li O

Ionic Bond Cation: Li Anion: O Li+ O2-

Ionic Bond Cation: Li Anion: O Li+ O2-

Ionic Bond Cation: Li Anion: O Li2O

MgO

Naming Ionic Compounds MgO Magnesium Oxide

NBr3

Naming Covalent Compounds NBr3 Nitrogen tribromide

Write the names and formulas… First! Decide if it’s ionic or covalent! Write names Na2O CO2 CaBr Na2CO3 Mg3P2 K2S N2S3 Write formulas Carbon monoxide Barium nitrate Xenon difluoride Carbon tetrachloride Sodium carbonate Lithium fluoride 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 types Electronegativity 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 Know Pure 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 I have no chance! 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 Find electronegativity of each atom

Electronegativity Chart

Example 1 Determine the type of bond in LiBr Find electronegativity of each atom Li = 1.0 Paulings, Br = 3.0 Paulings

Example 1 Determine the type of bond in LiBr Find electronegativity of each atom Li = 1.0 Paulings, Br = 3.0 Paulings Find Electronegativity Difference (∆EN) DEN = 3.0 – 1.0 = 2.0 Look at chart to determine bond type.

Moderately Polar Covalent 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 Find electronegativity of each atom Li = 1.0 Paulings, Br = 3.0 Paulings Find Electronegativity Difference (∆EN) DEN = 3.0 – 1.0 = 2.0 Look at chart to determine bond type. Bond Type: Ionic

Example 2 Determine the type of bond in O2 Find electronegativity of each atom

Electronegativity Chart

Example 2 Determine the type of bond in O2 Find electronegativity of each atom O = 3.4 Paulings, O = 3.4 Paulings

Example 2 Determine the type of bond in O2 Find electronegativity of each atom O = 3.4 Paulings, O = 3.4 Paulings Find Electronegativity Difference (∆EN) DEN = 3.4 – 3.4 = 0 Look at chart to determine bond type.

Moderately Polar Covalent 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 Find electronegativity of each atom O = 3.4 Paulings, O = 3.4 Paulings Find Electronegativity Difference (∆EN) DEN = 3.4 – 3.4 = 0 Look at chart to determine bond type. Bond Type: Nonpolar Covalent

CO 4. HF AlP 5. CaO N2 6. H2 How Polar Is It? Determine the polarity of each bond in the following compounds by calculating the electronegativity difference for each: CO 4. HF AlP 5. CaO N2 6. H2

Electronegativity Chart

Moderately Polar Covalent Bond Type Chart 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

Practice Time! Please finish the worksheet Then, 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.