Covalent BondingCovalent Bonding

Between nonmetalsBetween nonmetals Share valence electronsShare valence electrons between atoms between atoms

Electron clouds overlapElectron clouds overlap

Ex:Ex: HH22OO

CHCH44

NHNH33

COCO22

ElectronegativityElectronegativity

Difference in EN smaller than ionics and is Difference in EN smaller than ionics and is usually usually < 1.7< 1.7

Ex: Ex: HClHClH = 2.2H = 2.2 Cl = 3.2Cl = 3.2

Difference = 1.0Difference = 1.0

Bond PolarityBond Polarity Polar Bond:Polar Bond: there is a there is a

difference in EN values difference in EN values (unequal sharing)(unequal sharing)

Ex: H Ex: H Cl ClEN=2.2 EN=3.2EN=2.2 EN=3.2

NonPolar Bond:NonPolar Bond: no no difference in EN values. difference in EN values. (equal sharing)(equal sharing)

Ex: OEx: O22, N, N22, Cl, Cl22, H, H22

(all the diatomics!)(all the diatomics!)

Comparing Bond TypesComparing Bond Types

Single, Double, Triple BondsSingle, Double, Triple Bonds Atoms can Atoms can

share single share single double or triple double or triple bonds between bonds between them.them.

Each bond Each bond represents a represents a shared pair of shared pair of electrons.electrons.

http://youtu.be/1wpDicW_MQQ

Molecular FormulasMolecular Formulas

Covalent compounds are Covalent compounds are moleculesmolecules..Made up of all nonmetals.Made up of all nonmetals.

Molecular formulas:Molecular formulas: show actual number of show actual number of atoms of each element present in compoundatoms of each element present in compound

Ex: Ex: HH22OO

2 hydrogen atoms and 1 oxygen2 hydrogen atoms and 1 oxygen

Structural FormulasStructural Formulas

Show how the atoms are bonded together Show how the atoms are bonded together in a covalent molecule.in a covalent molecule.

Use “lines” to show covalent bondsUse “lines” to show covalent bonds

Empirical FormulasEmpirical FormulasShow Show simplest whole number ratiosimplest whole number ratio of atoms of atoms

or ions in the compound.or ions in the compound.

Ex: Ex: MgClMgCl22 1 : 2 ion ratio1 : 2 ion ratio

Ionic compounds are “Ionic compounds are “saltssalts” or ionic crystals. ” or ionic crystals. All ionic compounds All ionic compounds have empirical formulashave empirical formulas

You can simplify some molecular You can simplify some molecular formulas to make them empirical ratiosformulas to make them empirical ratios

Ex: Ex: CC66HH1212OO66

Simplest ratio of atoms CH2O

Naming Covalent CompoundsNaming Covalent CompoundsPrefix system indicates number of atoms of each elementPrefix system indicates number of atoms of each element

MonoMonoDiDiTriTriTetraTetraPentaPentaHexaHexaHeptaHeptaOctaOctaNonaNonaDecaDeca

Molecule vs. Ionic CrystalMolecule vs. Ionic Crystal

CH4 = 5 atoms in molecule NaCl = 1:1 ion ratioFormula Units vs. Molecules 7 minuteshttps://www.youtube.com/watch?v=dHWqJeSs8ms

Types of Chemical Formulas TutorialTypes of Chemical Formulas Tutorialhttps://www.youtube.com/watch?v=Y2eHJrZI

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Naming Tutorial (Ionic & Covalent) Naming Tutorial (Ionic & Covalent) https://www.youtube.com/watch?v=9XUsOLa

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Writing Formulas Tutorial (Ionic & Covalent)Writing Formulas Tutorial (Ionic & Covalent)https://www.youtube.com/watch?v=16agvZ8

K2eM

Drawing Covalent Drawing Covalent MoleculesMolecules

Lewis StructuresLewis Structures

See page 10 in Bonding PacketSee page 10 in Bonding Packet

1.1. Count total valence eCount total valence e-- in the molecule in the molecule

2.2. Draw molecule with single bonds between Draw molecule with single bonds between atoms atoms (then subtract these e- from total)(then subtract these e- from total)

3.3. Evenly distribute remaining eEvenly distribute remaining e-- in pairs to all in pairs to all atoms in molecule that still need e-atoms in molecule that still need e-

4.4. Check to see if all obey octet ruleCheck to see if all obey octet rule(Remember Hydrogen is fine with 2 e(Remember Hydrogen is fine with 2 e-- ) )

5.5. If deficient, shift over free eIf deficient, shift over free e-- pairs to make pairs to make double or triple bonds as needed.double or triple bonds as needed.

Draw NHDraw NH33

Draw HDraw H22OO

Draw CHDraw CH44

Crash Course Chemistry: Lewis Structures: (11 minutes)http://www.youtube.com/watch?v=a8LF7JEb0IA

Drawing Polyatomic IonsDrawing Polyatomic Ions

Covalently bonded atoms with a group chargeCovalently bonded atoms with a group charge Follow same steps for drawing covalents.Follow same steps for drawing covalents. Add or subtract electronsAdd or subtract electrons from total valence from total valence

depending on charge.depending on charge. Draw brackets around ion and indicate charge.Draw brackets around ion and indicate charge.

Ex:Ex: (SO(SO44) ) -2-2

6 + 4(6) + 2 = 32 electrons6 + 4(6) + 2 = 32 electrons

VSEPR and Molecular ShapeVSEPR and Molecular Shape

To To predict molecular shapepredict molecular shape, assume valence , assume valence electrons repel each other. electrons repel each other.

Molecule adopts 3D geometry that minimizes Molecule adopts 3D geometry that minimizes this repulsion.this repulsion.

VValence alence SShell hell EElectron lectron PPair air RRepulsion epulsion ((VSEPRVSEPR) theory.) theory.

Predicting Molecular Predicting Molecular GeometriesGeometries

Draw Lewis structureDraw Lewis structure Count total number of electron pairs around Count total number of electron pairs around

the central atom (both shared and unshared)the central atom (both shared and unshared) Arrange electron pairs to minimize eArrange electron pairs to minimize erepulsionrepulsion Multiple bounds count as one bonding pairMultiple bounds count as one bonding pair

Molecular ShapesMolecular Shapes

Regents Shapes to KnowRegents Shapes to Know::TetrahedralTetrahedralPyramidalPyramidalBentBentLinearLinear

Is a Molecule Polar?Is a Molecule Polar? If the centers of negative and positive If the centers of negative and positive

charge do not coincide, then the charge do not coincide, then the molecule is polar.molecule is polar.

Look for SymmetryLook for Symmetry Polar Molecules:Polar Molecules:

Have polar bonds and are Have polar bonds and are not symmetricalnot symmetricalPositive & negative “partial charges” don’t overlapPositive & negative “partial charges” don’t overlap

They have a “They have a “dipole momentdipole moment””

Nonpolar MoleculesNonpolar MoleculesHave nonpolar bondsHave nonpolar bonds

ORORHave polar bonds and are Have polar bonds and are symmetricalsymmetrical

Centers of positive & negative charge overlapCenters of positive & negative charge overlap

Example: Example: In COIn CO2,2, the polarity of each C-O bond is cancelled the polarity of each C-O bond is cancelled

because the molecule is linear. because the molecule is linear.

In HIn H22O, the polar H-O bonds do not cancel because O, the polar H-O bonds do not cancel because

the molecule is bent.the molecule is bent.

TetrahedralTetrahedral Has 4 atoms bonded Has 4 atoms bonded

(no free pairs)(no free pairs)

Symmetry?Symmetry?

Depends on what atoms are attached.

Can be polar (asymmetrical)

or nonpolar (symmetrical)

PyramidalPyramidalThree atoms bonded (one free pair)Three atoms bonded (one free pair)

Symmetry?Symmetry?

All pyramids are All pyramids are asymmetrical.asymmetrical.These molecules are always POLAR!These molecules are always POLAR!

BentBentTwo atoms attached (2 free pair)Two atoms attached (2 free pair)

The 2 free pair make it bent and not linear.The 2 free pair make it bent and not linear.

These are always asymmetrical so are always polar.

H2O

Hey, Water is Polar!!!!!Hey, Water is Polar!!!!!

Never forget this!!!

Without polar water NO LIFE!! Without polar water NO LIFE!! The polar nature of water molecules

allows them to bond to each other in groups and is associated with the high surface tension of water.

The polar nature of the water molecule has many implications. It causes water vapor at sufficient vapor pressure to depart from the ideal gas law because of dipole-dipole attractions. This can lead to condensation and phenomena like cloud formation, fog, the dewpoint, etc.

It also has a great deal to do with the function of water as the solvent of life in biological systems

LinearLinear2 atoms in molecule2 atoms in moleculeEx:Ex: ClCl Cl Cl (nonpolar bond, sym., nonpolar molecule)(nonpolar bond, sym., nonpolar molecule)

HH Br Br (polar bond, asym., polar molecule)(polar bond, asym., polar molecule)

3 atoms in molecule3 atoms in moleculeEx: CO2

GOOD FOR REVIEWGOOD FOR REVIEW

Crash Course Chemistry: Polarity of MoleculesCrash Course Chemistry: Polarity of Moleculeshttp://www.youtube.com/watch?v=PVL24HAesnc

Dipole Moment:Dipole Moment:https://www.khanacademy.org/science/organic-://www.khanacademy.org/science/organic-chemistry/gen-chem-review/electronegativity-chemistry/gen-chem-review/electronegativity-polarity/v/dipole-momentpolarity/v/dipole-moment

Properties of Covalent Properties of Covalent CompoundsCompounds

Melting PointMelting PointLower than IonicsLower than IonicsTo melt, you are only separating the weak To melt, you are only separating the weak

bonds bonds between moleculesbetween molecules (not within). (not within).

Melting PointMelting Point

Polar MoleculesPolar Molecules (dipoles/”mini-magnets”): (dipoles/”mini-magnets”):Have higher melting points than non-polars

because they are harder to separate.

SolubilitySolubility Polar MoleculesPolar Molecules dissolve in polar dissolve in polar

solvents as they are attracted to themsolvents as they are attracted to them like Hlike H22O, CHClO, CHCl33, NH, NH33 etc. etc.

Non-polar MoleculesNon-polar Molecules dissolve in dissolve in non-polar solvents non-polar solvents like hexane, CCllike hexane, CCl44

““Like Dissolves Like”Like Dissolves Like”

Oil and water Oil and water don’t mix!don’t mix!

How does soap How does soap work?work?

ConductivityConductivity

Covalent Molecules do not conduct well as Covalent Molecules do not conduct well as they they do not form ionsdo not form ions..They are “nonelectrolytes”They are “nonelectrolytes”

Except Acids!!!!Except Acids!!!! Acids are covalently bonded but in water (aqueous) they Acids are covalently bonded but in water (aqueous) they

will ionize and conduct current.will ionize and conduct current. (Acids are not on this test)(Acids are not on this test)

DecomposeDecompose

If the heat gets high enough If the heat gets high enough covalent compounds will covalent compounds will break down and decompose.break down and decompose.

(Remember the lab, sugar (Remember the lab, sugar melted first, then it burned and melted first, then it burned and turned into black carbon)turned into black carbon)

Other Types of Covalent Other Types of Covalent BondsBonds

Coordinate Covalent BondingCoordinate Covalent Bonding

Covalent bond in which Covalent bond in which oneone of the of the bonding atoms bonding atoms donates bothdonates both of the of the electrons to the bond.electrons to the bond.

The other atom donates nothing.The other atom donates nothing.

Ex: Forming Hydronium Ion

To form this type of To form this type of bond you must have:bond you must have:

A molecule with a free A molecule with a free pair of electronspair of electrons

Something that needs Something that needs to gain 2 electrons to gain 2 electrons H+1

Ex: Forming Ammonium IonEx: Forming Ammonium Ion

Network SolidsNetwork SolidsGiant network of covalently bonded atoms. Giant network of covalently bonded atoms. Large Large macromoleculesmacromoleculesExtremely strong structuresExtremely strong structures

Unusually high M.P. Unusually high M.P. Do not dissolveDo not dissolve

Diamonds are a giant network of carbon atoms.

“Buckyball”

Ex: Ex: C (s) (graphite, diamond, buckyball), C (s) (graphite, diamond, buckyball), SiOSiO22 (quartz), GeO (quartz), GeO22

Bonding in Pure MetalsBonding in Pure Metals

Metallic BondingMetallic Bonding

Happens in Happens in pure metals or alloys.or alloys.Ex:Ex: Mg, Fe, Brass, Au, Ni, CuMg, Fe, Brass, Au, Ni, Cu

““Delocalized” valence electrons move Delocalized” valence electrons move about about between all the metal atomsbetween all the metal atoms..

http://www.youtube.com/watch?v=XHV9LzCH2KA

Metallic BondingMetallic Bonding

PropertiesProperties Conducts heat and electricity very wellConducts heat and electricity very well

Conducts as a solid too!Conducts as a solid too!

Does not dissolve in solventsDoes not dissolve in solvents

Malleable and Ductile Malleable and Ductile

Relatively high melting point.Relatively high melting point.Higher MP than covalents.Higher MP than covalents.Similar MP to most ionicsSimilar MP to most ionics

Properties 2:00:http://www.youtube.com/watch?v=srxNJ03W_qM

What is a metal? 4:30https://www.youtube.com/watch?v=Xto88gMmDzw

Metallic BondingMetallic Bonding http://www.drkstreet.com/resources/metallic-bonding-http://www.drkstreet.com/resources/metallic-bonding-

animation.swfanimation.swf

EXTRA VIDEO LINKS FOR EXTRA VIDEO LINKS FOR FUN AND LEARNINGFUN AND LEARNING

Ionic vs. Covalent Bonding Ionic vs. Covalent Bonding http://youtu.be/QqjcCvzWwwwhttp://youtu.be/QqjcCvzWwwwhttp://youtu.be/yjge1WdCFPshttp://youtu.be/yjge1WdCFPs

ElectronegativityElectronegativityhttp://youtu.be/Kj3o0XvhVqQhttp://youtu.be/Kj3o0XvhVqQ

Bonding Dance PartyBonding Dance Partyhttp://www.youtube.com/watch?http://www.youtube.com/watch?v=wBCmt_pJTRAv=wBCmt_pJTRA

It’s a chemical bond baby”It’s a chemical bond baby”http://youtu.be/wWUYHHo-zB0http://youtu.be/wWUYHHo-zB0

Dancin Queen (Ionic/Covalent Bonds)Dancin Queen (Ionic/Covalent Bonds)http://youtu.be/BCYrNU-7SfAhttp://youtu.be/BCYrNU-7SfA

Isn’t it IonicIsn’t it Ionichttp://youtu.be/rwRtfrgJL5Ehttp://youtu.be/rwRtfrgJL5E