Chapter 8 and 9 notes.notebook - Mrs. Freeman's AP...

Chapter 8 and 9 notes.notebook

1

September 28, 2016

Sep 49:04 AM

Chapter 8Bonding

Sep 49:07 AM

BondingIonic Bonding: The bonding forces that result from the electrostatic attractions of the closely packed. oppositely charged ions.

Ionic Compounds: When a metal reacts with a nonmetalProperties:• Hard• Form Crystal Lattices• Good Insulators• High Melting/Boiling Points• Conduct Electricity when dissolved in water or as a liquid

• Does not conduct electricity as a solid


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September 28, 2016

Aug 269:11 AM

Bonding

Coulomb's Law: The energy of interaction between a pair of ions

F = Q1Q2r2( )

Q the charges of the particlesr distance between the center of the atoms

Lattice Energy: The change in energy that takes place when separated gaseous ions are packed together to form an ionic solid

Ionic Compounds

Sep 49:16 AM

Covalent Bonding: A type of bonding in which electrons are shared

Covalent Compounds: When a nonmetal reacts with another nonmetal

Bonding

Propeties

• Soft, tend to be gases, liquids or soft (brittle) solids

• Poor conductors of heat and electricity

• Molecules (Not lattices)

• Nonelectrolytesdo not conduct electricity in water


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September 28, 2016

Sep 410:48 AM

BondingLocalized Electron Bonding Model: Assumes that a molecule is composed of atoms that are bound together by sharing pairs of electrons using the atomic orbitals of the bound atoms

Lone Pairs: Pairs of electrons localized on an atom

Bonding Pairs: Electrons found in the space between the atoms

Sep 410:59 AM

BondingLewis Structures: Show how the valance electrons are arranged among the atoms in the molecule

Octet RuleOnly valance electrons are shown


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September 28, 2016

Sep 410:59 AM

Bonding1. Add up the valence electrons from all of the atoms involved. 2. use a pair of electrons to form bonds between each pair of bonded atoms (Central atom!)3. Arrange the remaining electrons to satisfy the octet rule (remember there are exceptions to the rule!) (Distribute to the outside atoms first!)4. Make double/triple bonds as needed

Sep 410:59 AM

BondingExceptions to the Octet Rule:Hydrogen only holds two electrons at mostBoron will only hold three pairs of electrons (6 in total instead of 8)Atoms with access to the DSubshell can hold more than 8

CH4, PCl3, SiF4, CO2, SO2, BBr3, ClF5, KrI2, PBr5


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September 28, 2016

Sep 221:47 PM

BondingBond Length is the distance at which the system has minimum energy...It is the length between two atoms.

Single > Double > Triple (halves will fit in between)

Bond Order: How many bonds (Single, double, triple, and halves) are between two atoms

Sep 410:59 AM

BondingResonance Structures: All of the structures possible for a particular molecule

Resonance: invoked when more than on valid Lewis structure can be written for a particular molecule

The actual structure is an average of these structures


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September 28, 2016

Sep 411:26 AM

BondingFormal Charge: Used to determine stability of possible resonance structures.

SO

OO

O[ ]2

SO

OO

O[ ]2

Formal Charge = # of valance electrons (# of lone electrons + 1/2 # of bonded electrons)

• Formal charges are best when closest to 0• When the negative charge is on the most electronegative atom

Formal Charges should all add up to be 0 if the molecule is neutral or the charge of the molecule if it is not neutral

S = 6(0+1/2(8)) S = 64 S = 2O = 6(6+1/2(2)) O = 67 O=1

S = 6 (0 + 1/2(12)) S = 66 S= 0O = 6 (6 + 1/2(2) O = 67 O=1O = 6 (4 + 1/2(4) O = 66 O= 0

Sep 411:26 AM

BondingGive all the possible Lewis Structures for XeO3, an explosive compound of xenon. which Lewis Structure or structures are most appropriate according to the formal charges


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September 28, 2016

Sep 138:55 AM

Sep 221:39 PM

BondingCoulomb's Law: The energy of interaction between a pair of ions (leads to bond strength)

F = Q1Q2r2( )

Q the charges of the particlesr distance between the center of the atoms

http://phet.colorado.edu/en/simulation/atomic-interactions


8

September 28, 2016

Sep 49:24 AM

BondingBond energy: The energy required to break the bond (Endothermic Process!) (Therefore forming bonds is an Exothermic Processreleases energy)

Coulombs law dictates the average energy values that we see here! (bond length and change differences)

Aug 278:57 AM

H2 + F2 > 2HFHH = 432 KJ/mol FF = 154 KJ/mol HF = 565 KJ/mol

BondingEnthalpy (ΔH)The total energy of a system (or reaction)

ΔH = ΣD(Bonds Broken) ΣD(Bonds Formed)

D is the positive bond energy per mole

(Why do you think the bond energies are so different for HH, FF, and HF?)


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September 28, 2016

Aug 278:35 AM

Use bond energies to determine what the reaction enthalpy is for the following reaction:

Sep 411:26 AM

Bonding

VSEPR Model (Valence Shell ElectronPair Repulsion Model): Used to predict the approxiamte molecular structure of a molecule

Molecular Structure: The 3D arrangement of the atoms in a molecule

The structure around a given atom is determined principally by minimizing electronpair repulsion


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September 28, 2016

Sep 88:24 AM

BondingLinear:

Sep 88:24 AM

BondingTrigonal Planar:


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September 28, 2016

Sep 88:24 AM

BondingTetrahedral:

Sep 88:24 AM

BondingTrigonal Bipyramidal


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September 28, 2016

Sep 88:24 AM

BondingOctahedral

Sep 1212:31 PM


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September 28, 2016

Sep 41:51 PM

BondingHybridization and the Localized Electron Model

Hybridization The mixing of the native atomic orbitals to form special orbitals for bonding

CH4 1s2s22p21s2Hydrogen: Carbon:

Sigma Bond (σ): Electron pair that is shared in an area centered on a line running between the two atoms (Single bonds)

Oct 111:33 AM

BondingSigma Bonding: Single bonding area

Pi Bonding: Double bonding area


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September 28, 2016

Sep 42:09 PM


C2H4 C CH

H

H

H

SP2 Hybridization

Pi Bonds (π) : The parallel p orbitals can share an electron pair . This occupies the space above and below a line joining the atoms (Double/Triple Bonds)

Sep 42:20 PM


SP Hybridization

CO O

CO2


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September 28, 2016

Sep 43:09 PM

BondingFor NH3, CO, BF4

(Does obey the octet), and XeF2: draw the Lewis dot structure, determine the vsepr shape and geometry, and state the central atom's hybridization

Sep 39:22 AM

Organic Naming


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September 28, 2016

Sep 39:21 AM

Functional groups

Sep 49:24 AM

BondingElectronegativity: the ability of an atom in a molecule to attract shared electrons to itself


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September 28, 2016

Sep 410:12 AM

Bonding

The electronegativity of a bond can be determined using the Pauling Values in the above periodic table. He found these by taking the average of the bond energies of the elements in the bond.

Linus Pauling (19011995)

HF HH4.0 2.1 = 1.9 2.1 2.1 = 0

Covalent Polar Covalent IonicE Values: 0 1.7 3.5

Sep 410:21 AM

BondingOrder the following bonds according to polarity: HH, OH, ClH, SH, FH

HH < SH < ClH < OH < FH


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September 28, 2016

Sep 1112:50 PM

BondingDipole Moments:

Within a molecule there is a charge distribution so that there is a positive end and a negative end.

Commonly shown by an arrow pointing in the negative direction (the most electronegative atom in the bond)

H F

Sep 222:30 PM

BondingIntramolecular forces: chemical bonds that hold two or more atoms together

Intermolecular forces: interactions and attractions between the molecules (not within)

Phase changes are due to the breaking and forming of the intermolecular forces


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September 28, 2016

Oct 211:58 AM

BondingDipoleDipole attraction: Molecules with dipole moments can attract each other electrostatically lining up so that the positive and negative ends are close to each other.

Remember that a dipole moment is when a molecule has a positive and negative end due to the electronegativity inside the compound.

Remember this is what makes molecules polar or nonpolar.

Oct 212:00 PM

DipoleDipole attraction

These bonds are 1% the strength of a covalent or ionic Intramolecular bond

They become weaker as the distance between the dipoles increases

Gas phase, where the molecules are far apart, these forces are relatively unimportant

Bonding


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September 28, 2016

Oct 212:00 PM

BondingHydrogen bonds: A particularly strong dipoledipole force, where hydrogen is bonded to a highly electronegative atom such as nitrogen, oxygen or fluorine

Two reasons these forces are strong

1. The great polarity of the bonds

2. the size of the hydrogen ion allows for the dipoles to be close together

Oct 212:00 PM

BondingHydrogen bonds

Remember that these intermolecular forces are what are breaking during phase change. The strong the bond the higher the temperature it is to break that intermolecular force

Group 4A has a steady increase in boiling points as you go down the group

Groups 5A, 6A, and 7A have the highest boiling point at the top of their group.

>This is because of the electronegativity (hydrogen bonds)and the relative size of the atoms in the bond


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September 28, 2016

Oct 212:01 PM

London Dispersion Forces: This is the force found in the noble gases and nonpolar molecules. This occurs when a temporary dipole moment happens

As the electrons move around an atom or around a molecule a momentary nonsymmetrical electron distribution can occur

This creates a temporary dipole moment in one atom or molecule which in turns induces a dipole moment in the atoms or molecules around it.

This attraction is relatively weak and short lived

Bonding

Oct 212:01 PM

For the formation of a solid, the motion of the atoms must be slowed down greatly which is why the noble gases have such low freezing points.

We see an increase in freezing point down the Noble gas family due to the increase in electrons. This increase leads to the increased chance of momentary dipole interactions.

>Polarizability: The ease with which the electron "Cloud" of an atom can be distorted to give a dipolar charge distribution.

Bonding


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September 28, 2016

Oct 212:01 PM

Explain what is well represented and poorly represented in each model

Oct 212:01 PM


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September 28, 2016

Oct 212:01 PM

Oct 212:01 PM

Chapter 8 and 9 notes.notebook - Mrs. Freeman's AP...

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