7 2 Molecular Geometry and Polarity Molecular polarity

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7. 2 Molecular Geometry and Polarity Molecular polarity is one of the most important

7. 2 Molecular Geometry and Polarity Molecular polarity is one of the most important consequences of molecular geometry. A diatomic molecule is polar when the electronegativites of the two atoms are different. • • H−F • • δ− • • H−F • • δ+

Molecular Geometry and Polarity The polarity of a molecule made up of three or

Molecular Geometry and Polarity The polarity of a molecule made up of three or more atoms depends on: (1) the polarity of the individual bonds (2) the molecular geometry Carbon dioxide, CO 2 The bonds in CO 2 are polar but the molecule is nonpolar.

Molecular Geometry and Polarity The polarity of a molecule made up of three or

Molecular Geometry and Polarity The polarity of a molecule made up of three or more atoms depends on: (1) the polarity of the individual bonds (2) the molecular geometry Water, H 2 O The bonds in H 2 O are polar and the molecule is polar.

Molecular Geometry and Polarity The polarity of a molecule made up of three or

Molecular Geometry and Polarity The polarity of a molecule made up of three or more atoms depends on: (1) the polarity of the individual bonds (2) the molecular geometry Boron trifluoride, BF 3 The bonds in BF 3 are polar but the molecule is nonpolar.

Worked Example 7. 3 (a) Determine whether PCl 5 is polar. Strategy Draw the

Worked Example 7. 3 (a) Determine whether PCl 5 is polar. Strategy Draw the Lewis structure, use the VSEPR model to determine its molecular geometry, and then determine whether the individual bond dipoles cancel. (a) The Lewis structure of PCl 5 is

Worked Example 7. 3 (b) Determine whether (b) H 2 CO (C double bonded

Worked Example 7. 3 (b) Determine whether (b) H 2 CO (C double bonded to O) is polar. Strategy Draw the Lewis structure, use the VSEPR model to determine its molecular geometry, and then determine whether the individual bond dipoles cancel. (b) The Lewis structure of H 2 CO is • https: //phet. colorado. edu/en/simulation/molecule-polarity

Molecular Geometry and Polarity Dipole moments can be used to distinguish between structural isomers.

Molecular Geometry and Polarity Dipole moments can be used to distinguish between structural isomers. trans-dichloroethylene nonpolar cis-dichloroethylene polar

7. 3 Intermolecular Forces Intermolecular forces are attractive forces between neighboring molecules. These forces

7. 3 Intermolecular Forces Intermolecular forces are attractive forces between neighboring molecules. These forces are known collectively as van der Waals forces. ØThe magnitude (and type) of intermolecular forces can be sufficient to hold the molecules of a substance together in a solid or liquid. ØGases have no apparent intermolecular forces

Dipole-Dipole Interactions Dipole-dipole interactions are attractive forces that act between polar molecules. The magnitude

Dipole-Dipole Interactions Dipole-dipole interactions are attractive forces that act between polar molecules. The magnitude of the attractive forces depends on the magnitude of the dipole. ØRed is high electron density (δ-) and blue is low (δ+)

Intermolecular Forces

Intermolecular Forces

Hydrogen Bonding Hydrogen bonding is a special type of dipole-dipole interaction. Hydrogen bonding only

Hydrogen Bonding Hydrogen bonding is a special type of dipole-dipole interaction. Hydrogen bonding only occurs in molecules that contain H bonded to a small, highly electronegative atom such as N, O, or F. F H F Text Practice: 7. 32

Dispersion Forces Dispersion forces or London dispersion forces result from the Coulombic attractions between

Dispersion Forces Dispersion forces or London dispersion forces result from the Coulombic attractions between instantaneous dipoles of non-polar molecules. Text Practice: 7. 23 7. 24 7. 26 7. 28

Intermolecular Forces

Intermolecular Forces

Hydrogen Bonding

Hydrogen Bonding

Worked Example 12. 1 What kind(s) of intermolecular forces exist in (a) CCl 4(l),

Worked Example 12. 1 What kind(s) of intermolecular forces exist in (a) CCl 4(l), (b) CH 3 COOH(l), (c) CH 3 COCH 3(l), and (d) H 2 S(l). Strategy Draw Lewis dot structures and apply VSEPR theory to determine whether each molecule is polar or nonpolar. Nonpolar molecules exhibit dispersion forces only. Polar molecules exhibit dipole-dipole interactions and dispersion forces. Polar molecules with N–H , F–H, or O–H bonds exhibit dipole interactions (including hydrogen bonding) and dispersion forces. (a) (b) (c) (d)

Ion-Dipole Interactions Ion-dipole interactions are Coulombic attractions between ions (either positive or negative) and

Ion-Dipole Interactions Ion-dipole interactions are Coulombic attractions between ions (either positive or negative) and polar molecules.

5. 7 Covalent Bonding in Ionic Species Polyatomic ions such as PO 43 -

5. 7 Covalent Bonding in Ionic Species Polyatomic ions such as PO 43 - consist of a combination of two or more atoms bonded covalently. Formulas are determined following the same rule as for ionic compounds containing only monatomic ions: ions must combine in a ratio that give a neutral formula overall. Calcium phosphate: Ca 2+ PO 43– Ca 3(PO 4)2 Sum of charges: 3(+2) + 2(– 3) = 0

Covalent Bonding in Ionic Species

Covalent Bonding in Ionic Species

Covalent Bonding in Ionic Species

Covalent Bonding in Ionic Species

Hydrates A hydrate is a compound that has a specific number of water molecules

Hydrates A hydrate is a compound that has a specific number of water molecules within its solid structure. For example, in its normal state, copper(II) sulfate has five water molecules associated with it. Systematic name: copper(II) sulfate pentahydrate Formula: Cu(SO)4 ∙ 5 H 2 O Some other hydrates are Ba. Cl 2 ∙ 2 H 2 O Li. Cl ∙ H 2 O Mg. SO 4 ∙ 7 H 2 O Sr(NO 3)2 ∙ 4 H 2 O

Hydrates When the water molecules are driven off by heating, the resulting compound, Cu(SO)4,

Hydrates When the water molecules are driven off by heating, the resulting compound, Cu(SO)4, is sometimes called anhydrous copper(II) sulfate. Anhydrous means the compound no longer has water molecules associated with it. Cu(SO)4 is white Cu(SO)4 ∙ 5 H 2 O is blue

Familiar Inorganic Compounds Text Practice: 5. 62

Familiar Inorganic Compounds Text Practice: 5. 62

Study Guide for Sections 7. 2 -7. 3, 5. 7 DAY 14, Terms to

Study Guide for Sections 7. 2 -7. 3, 5. 7 DAY 14, Terms to know: Sections 7. 2 -7. 3, 5. 7: molecular geometry, bond angle, molecular polarity, intermolecular forces (van der Waals forces), dipole-dipole interactions, hydrogen bonding, London forces, polarizability, instantaneous dipole, induced dipole, ion-dipole, polyatomic ions, hydrate, anhydrous DAY 14, Specific outcomes and skills that may be tested on exam 2: Sections 7. 2 -7. 3, 5. 7 • Be able to determine direction and relative magnitude of overall molecular polarity by analyzing molecular geometry, individual bond polarities, and formal charges • Be able to list the types of intermolecular forces that exist and give examples of molecules that would have those forces of attractions and WHY • Given a molecular formula or a Lewis structure, be able to determine what types of intermolecular forces would likely to be present between two molecules • Be able to explain how hydrogen bonds are different from covalent bonds and how they are different from other types of dipole-dipole attractions • For a given set of molecules, rank them in order of increasing strengths of intermolecular attractions • Given a formula including a polyatomic ion, be able to predict which atoms present are bonded through ionic bonds and which atoms are bonded through covalent bonds • Be able to predict the chemical formula for an ionic compound involving polyatomic ions • Be able to recognize hydrates, write and read their formulas, and describe the attractions present in hydrates

Extra Practice Problems for Sections 7. 2 -7. 3, 5. 7 Complete these problems

Extra Practice Problems for Sections 7. 2 -7. 3, 5. 7 Complete these problems outside of class until you are confident you have learned the SKILLS in this section outlined on the study guide and we will review some of them next class period. 7. 19 7. 21 7. 33 7. 39 7. 105 (c and d) 7. 107 7. 111 b 12. 91

Prepare for Day 16 Must Watch videos: https: //www. youtube. com/watch? v=f. IMd. IMACy.

Prepare for Day 16 Must Watch videos: https: //www. youtube. com/watch? v=f. IMd. IMACy. N 4 (KMT, Tyler De. Witt) https: //www. youtube. com/watch? v=ap. OSDq. Zd 6 Fg (KMT, Tyler De. Witt) https: //www. youtube. com/watch? v=zvh 9 uv 2 Hxx 4 (gas pressure, Tyler De. Witt) https: //www. youtube. com/watch? v=TLRZAFU_9 Kg (gasses, crash course chemistry) Other helpful videos: http: //www. youtube. com/watch? v=f 8 qr. UJg. P 42 Y (KMT, Brightstorm) http: //echem 1 a. cchem. berkeley. edu/modules/module-6/ (UV-Berkeley, lesson 17) Read Sections 11. 1 -11. 2, 5. 8, 11. 3