Chapter 4: Chapter 4: Chemical BondingChemical Bonding

When Atoms CollideWhen Atoms Collide

Today’s ObjectivesToday’s Objectives

To be able to:To be able to:• Explain why some elements react (form bonds.)Explain why some elements react (form bonds.)

• Explain the difference between an ionic & a Explain the difference between an ionic & a covalent bond.covalent bond.

• Demonstrate e- reconfiguration when a simple Demonstrate e- reconfiguration when a simple compound is formed.compound is formed.

Sodium (metal)Sodium (metal)

SolidSolid Good conductor of electricity & heatGood conductor of electricity & heat VERY reactiveVERY reactive Silvery/lusterSilvery/luster Malleable, softMalleable, soft Melting point-low 98 CMelting point-low 98 C Uses: never pure in nature b/c sooooo Uses: never pure in nature b/c sooooo

reactive!reactive!

Chlorine (nonmetal)Chlorine (nonmetal)

Poisonous, green gasPoisonous, green gas DisinfectantDisinfectant Reactivity-very reactive. Rarely found pure Reactivity-very reactive. Rarely found pure

in nature b/c sooo reactive.in nature b/c sooo reactive.

Salt (NaCl)Salt (NaCl)

Edible, common food additiveEdible, common food additive WhiteWhite Crystalline solidCrystalline solid Reactivity-not reactive/ very stableReactivity-not reactive/ very stable BrittleBrittle Conductivity- as a solid, poor conductorConductivity- as a solid, poor conductor

As a liquid or in aqueous solution, excellent As a liquid or in aqueous solution, excellent conductor = ELECTROLYTEconductor = ELECTROLYTE

Carbon (nonmetal)Carbon (nonmetal)

Solid @ room temperatureSolid @ room temperature Fairly unreactive @ rm temperature. Very Fairly unreactive @ rm temperature. Very

reactive at high temperatures.reactive at high temperatures. Most of the compounds in living things made Most of the compounds in living things made

from carbon.from carbon. Brittle/hard (charcoal/diamond)Brittle/hard (charcoal/diamond) High melting & boiling pointsHigh melting & boiling points

Oxygen (Nonmetal)Oxygen (Nonmetal)

Gas at room tempGas at room temp Colorless, odorless, tastelessColorless, odorless, tasteless 21% of atmosphere21% of atmosphere Very low MP/BP (-183 C BP)Very low MP/BP (-183 C BP) Slightly soluble in waterSlightly soluble in water Reactive, combines w/many elementsReactive, combines w/many elements Most abundant element in earth’s crustMost abundant element in earth’s crust

Carbon dioxideCarbon dioxide

Somewhat soluble in waterSomewhat soluble in water Poor conductorPoor conductor Fairly unreactive Fairly unreactive UsesUses

some fire extinguisher b/c it won’t burnsome fire extinguisher b/c it won’t burn PhotosynthesisPhotosynthesis

Nearly all the food for all living things comes thru Nearly all the food for all living things comes thru photosynthesisphotosynthesis

Trees pull COTrees pull CO22 out of the air & decrease greenhouse effect out of the air & decrease greenhouse effect

HydrogenHydrogen

Odorless, tasteless, colorlessOdorless, tasteless, colorless Very reactive (ex: Hindenburg)Very reactive (ex: Hindenburg) Low MP & BPLow MP & BP Gas at rm temperatureGas at rm temperature Slightly soluble in waterSlightly soluble in water not a conductornot a conductor Lightest and most abundant element in Lightest and most abundant element in

universeuniverse

WaterWater

Liquid at room tempLiquid at room temp Stable-doesn’t react w/most thingsStable-doesn’t react w/most things examplesexamples

Chemical rxns in human body take place in Chemical rxns in human body take place in waterwater

`Necessary for photosynthesis`Necessary for photosynthesis

ClassworkClasswork

On p 59 of I.N.On p 59 of I.N.

Analyze CO2Analyze CO2 Compare the properties of C, O, Compare the properties of C, O,

and CO2and CO2

What is Happening?What is Happening?

Watch the videos.Watch the videos. What is What is

happening in all happening in all of these of these reactionsreactions??

Hydrogen balloon burning2H2 + O2 2H2O

sodium metal & chlorineNa + Cl NaCl

sodium iodide & mercury (II) chloride2NaI + HgCl2 2NaCl + HgI2

When Atoms Combine to Form When Atoms Combine to Form CompoundsCompounds

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

Stable “Happy” AtomsStable “Happy” Atoms

Have Noble Gas Configuration (NGC)Have Noble Gas Configuration (NGC)

8 valence electrons8 valence electrons

OR 2 valence electrons if only the 1st OR 2 valence electrons if only the 1st energy level is occupied (Like He) energy level is occupied (Like He)

ACTIVITY: Egg Carton AtomsACTIVITY: Egg Carton AtomsIonic BondingIonic Bonding

MATERIALSMATERIALS Egg carton (“atom”)Egg carton (“atom”)

Candy or marbles (“electrons”)Candy or marbles (“electrons”)

Data SheetData Sheet

Rules for “Placing” e-sRules for “Placing” e-s Place e-s in lowest Place e-s in lowest

available E.L.available E.L.

Fill an E.L. before Fill an E.L. before putting e-s in next putting e-s in next available E.L.available E.L.

Only 1 “electron” per Only 1 “electron” per space in egg carton.space in egg carton.

Your Goal:”Happy” AtomsYour Goal:”Happy” AtomsIonic CompoundIonic Compound

With your partner, obtain NGC for BOTH of With your partner, obtain NGC for BOTH of your atoms!your atoms!

Each atom will have EITHEREach atom will have EITHER A full 1st E.L. & no e-s in 2nd E.L. ORA full 1st E.L. & no e-s in 2nd E.L. OR A full 1st and 2nd E.L.A full 1st and 2nd E.L.

One will donate e-s & one will receive e-s.One will donate e-s & one will receive e-s.

Step 1: Your AtomStep 1: Your Atom Count # of “e-s”Count # of “e-s” Identify elementIdentify element Identify column/group#Identify column/group# What is valence What is valence levellevel?? How many valence e-s?How many valence e-s? How many e-s must be How many e-s must be

gained to obtain NGC?gained to obtain NGC? How many e-s must be lost to How many e-s must be lost to

obtain NGC?obtain NGC? How many e-s lost or gained How many e-s lost or gained

(Which is easier?)(Which is easier?)

DATA TA BLE: Ionic Bonding IIMY AT OM PARTNER’S

ATOMTotal # of e-sElementColumn (Group#)Valence level# of valence e-s# of e-s I needto gain to getNGC# of e-s I needto lose to getNGC# of e’slost/gainedCompoundformed

Step 2: Both AtomsStep 2: Both Atoms

Share your information with your partner & record on Data Table.Share your information with your partner & record on Data Table.

Decide how you can help each other obtain NGC by giving or Decide how you can help each other obtain NGC by giving or receiving e-s.receiving e-s.

Make the e- switch! & observe NGC.Make the e- switch! & observe NGC.

Step 3: Discuss ResultsStep 3: Discuss Results

DATA TA BLE: Ionic Bonding IMY AT OM PARTNER’S

ATOMTotal # of e-s 4 8Element Be OColumn (Group#)

2 16

Valence level 2nd 2nd

# of valence e-s 2 6# of e-s I needto gain to getNGC

6 2

# of e-s I needto lose to getNGC

2 6

# of e’slost/gained

2 lost 2 gained

Compoundformed

BeO BeO

Now it’s your turn!Now it’s your turn! With your new set of “electrons,” form an ionic compound with With your new set of “electrons,” form an ionic compound with

your partner.your partner.

Record your data and your partner’s.Record your data and your partner’s.

Be prepared to discuss.Be prepared to discuss.

Results of Example 2: Li & OResults of Example 2: Li & ODATA TA BLE: Ionic Bonding II

MY AT OM PARTNER’SATOM

Total # of e-s 3 9Element Li FColumn (Group#)

1 17

Valence level 2nd 2nd

# of valence e-s 1 7# of e-s I needto gain to getNGC

7 1

# of e-s I needto lose to getNGC

1 7

# of e’slost/gained

1 lost 1 gained

Compoundformed

LiF LiF

So what about the bond?So what about the bond? When e-s are lost or When e-s are lost or

gained, the atom develops gained, the atom develops a charge and becomes an a charge and becomes an ion.ion.

Attraction between ions is Attraction between ions is what forms bond.what forms bond.

Note: you will not always Note: you will not always have a 1:1 ratio of + to - have a 1:1 ratio of + to - ions.ions. Ex: MgI2-see next slideEx: MgI2-see next slide

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

Formation of MgI2Formation of MgI2

.... .. .. ..MgMg. +. + :I: → Mg. + :I: (are they happy?) :I: → Mg. + :I: (are they happy?)

.. .. ..

.. .... .. .. .. .. .. ..MgMg. +. + :I: :I: :I: → Mg + :I: :I::I: → Mg + :I: :I:

.. . . .. .. .. ..

3 “Classes” of Elements3 “Classes” of Elements Metals =Metals = pinkpinkConductors? Conductors? Yes!Yes!Hold e-s? Hold e-s? LooselyLooselyHow many V.E’s? How many V.E’s? 1-31-3

Nonmetals =Nonmetals = greengreenConductors? Conductors? No!No!Hold e-s? Hold e-s? TightlyTightlyHow many V.E.’s? How many V.E.’s? 5-75-7

Metalloids =Metalloids = blueblue““In between”In between”

Ionic BondingIonic Bonding

Typically occurs between a Typically occurs between a metalmetal (“weak”) & (“weak”) & a a nonmetalnonmetal (“strong”) (“strong”)

MetalMetal loses e-s, forming a + ion (cation) loses e-s, forming a + ion (cation)

Nonmetal Nonmetal gains e-s, forming a - ion (anion)gains e-s, forming a - ion (anion)

Covalent BondingCovalent Bonding

Involves the sharing of electrons.Involves the sharing of electrons.

Occurs when the 2 atoms involved are Occurs when the 2 atoms involved are close in “strength” (pull on e-s)close in “strength” (pull on e-s)

Usually occurs betweenUsually occurs between 2 2 nonmetalsnonmetals

Activity: Egg Carton AtomsActivity: Egg Carton AtomsCovalent BondingCovalent Bonding

Your Goal: With your partner, Your Goal: With your partner, obtain NGC for both your obtain NGC for both your atoms by atoms by sharingsharing electrons! electrons!

NOTE: Overlap cartons to NOTE: Overlap cartons to represent sharing of e-s.represent sharing of e-s.

Practice Together: HPractice Together: H22

Each partner is going Each partner is going to represent a H atom.to represent a H atom.

Let’s answer the Qs Let’s answer the Qs together. together.

DATA TA BLE: Covalent Bonding: H2

MY AT OM PARTNER’SATOM

Total # of e-sElementColumn (Group#)Valence level# of valence e-s# of e-s I needto gain to getNGC# of rows tooverlap# of e’s gainedCompoundformed

Step 2: Both AtomsStep 2: Both Atoms Remove “e-s” from rows that will be Remove “e-s” from rows that will be

overlapped.overlapped.

Overlap 1 carton’s row/s with your Overlap 1 carton’s row/s with your partner’s.partner’s.

Place the removed e-s from both atoms Place the removed e-s from both atoms in the overlapped rows. -NGC!in the overlapped rows. -NGC!

Step 1: Your Atom, FStep 1: Your Atom, F Count # of “e-s”Count # of “e-s” Identify elementIdentify element Identify column/group#Identify column/group# What is valence What is valence levellevel?? How many valence e-s?How many valence e-s? How many e-s must be How many e-s must be

gained to obtain NGC?gained to obtain NGC? This is the # of rows that This is the # of rows that

must be overlapped to must be overlapped to share e-s with your share e-s with your partner. partner.

DATA TA BLE: Covalent Bonding: F2

MY AT OM PARTNER’SATOM

Total # of e-s 9 9Element F FColumn (Group#)

17 17

Valence level 2 2# of valence e-s 7 7# of e-s I needto gain to getNGC

1 1

# of rows tooverlap

1 1

# of e’s gained 1 1Compoundformed

F2 F2

Step 2: Both AtomsStep 2: Both Atoms

Remove “e-s” from rows that will be overlapped.Remove “e-s” from rows that will be overlapped.

Overlap 1 carton’s row/s with your partner’s.Overlap 1 carton’s row/s with your partner’s.

Place the removed e-s from both atoms in the Place the removed e-s from both atoms in the overlapped rows. -NGC!overlapped rows. -NGC!

SolutionSolution

DATA TA BLE: Covalent Bonding: F2

MY AT OM PARTNER’SATOM

Total # of e-s 9 9Element F FColumn (Group#)

17 17

Valence level 2 2# of valence e-s 7 7# of e-s I needto gain to getNGC

1 1

# of rows tooverlap

1 1

# of e’s gained 1 1Compoundformed

F2 F2

More PracticeMore Practice

Each person makes their atom.Each person makes their atom. Next form covalent compound with Next form covalent compound with

neighbor.neighbor. OxygenOxygen

NitrogenNitrogen

Answers to practiceAnswers to practice

Oxygen involves the overlap of 2 rows in Oxygen involves the overlap of 2 rows in each carton. (double bond)each carton. (double bond)

Nitrogen involves the overlap of 3 rows in Nitrogen involves the overlap of 3 rows in each carton. (triple bond)each carton. (triple bond)

QuizQuiz

Ionic bonds are formed Ionic bonds are formed by the ______ of by the ______ of electrons.electrons.

Covalent bonds are Covalent bonds are formed by the formed by the ________ of electrons.________ of electrons.

CO is a/n CO is a/n ionic/covalent ionic/covalent compound.compound.

NaF is a/n NaF is a/n ionic/covalent ionic/covalent compound.compound.

Summary so FarSummary so Far Atoms that collide may bond if they can help each Atoms that collide may bond if they can help each

other become more stable.other become more stable. Noble gases are stable the way they are-8 valence Noble gases are stable the way they are-8 valence

e-s in most cases (“octet”).e-s in most cases (“octet”). All other elements want to be like noble gases.All other elements want to be like noble gases. Two ways to get “NGC”Two ways to get “NGC”

Transfer e-s if strength of 2 elements is very unequal Transfer e-s if strength of 2 elements is very unequal (ionic bond)(ionic bond)

Share e-s if strength of 2 elements is pretty equal Share e-s if strength of 2 elements is pretty equal (covalent bond)(covalent bond)

““Isoelectronic”Isoelectronic”

Term used to describe atoms/ions with the Term used to describe atoms/ions with the same electron configurationsame electron configuration

Ex: F- and NeEx: F- and Ne Both have 2 e-s in the 1Both have 2 e-s in the 1stst energy level energy level Both have 8 electrons in the 2Both have 8 electrons in the 2ndnd energy level energy level

Ex: He and H-Ex: He and H- Both have 2 electrons in the exact same Both have 2 electrons in the exact same

arrangementarrangement

FormulasFormulas

TellsTells the elements that make up the compoundthe elements that make up the compound the # of atoms of each element in a unit of the the # of atoms of each element in a unit of the

compoundcompound

““Formula Unit” v. MoleculeFormula Unit” v. Molecule Formula Unit applies to all compoundsFormula Unit applies to all compounds Molecule applies ONLY TO COVALENT Molecule applies ONLY TO COVALENT

COMPOUNDSCOMPOUNDS

To Explain Why…To Explain Why…

Elements in an ionic compound occur in a Elements in an ionic compound occur in a specific ratio, BUTspecific ratio, BUT

You never have just 1 Na and 1 Cl, for You never have just 1 Na and 1 Cl, for exampleexample

Instead YOU HAVE A CRYSTALLINE Instead YOU HAVE A CRYSTALLINE STRUCTURE (“lattice”) (see p 134)STRUCTURE (“lattice”) (see p 134)

Crystal Arrangement Causes Crystal Arrangement Causes Behavior of Ionic CompoundsBehavior of Ionic Compounds

Each ion is “locked in”Each ion is “locked in” This makes ionic compoundsThis makes ionic compounds

Very stableVery stable Solids (high MP, BP.)Solids (high MP, BP.) BrittleBrittle Cubic in shapeCubic in shape

The attraction between formula units (particles of a substance) is The attraction between formula units (particles of a substance) is called: “INTERPARTICLE FORCES”called: “INTERPARTICLE FORCES”

In addition, ionic compounds areIn addition, ionic compounds are Very soluble in waterVery soluble in water good conductors of electricity-WHY???good conductors of electricity-WHY???

e Fig 22-25 p 570

Ionic Compounds-Good ConductorsIonic Compounds-Good Conductors

In order for something to be a good In order for something to be a good conductor, it must have freely moving conductor, it must have freely moving charged particles.charged particles.

Ions are charged particles that are “locked Ions are charged particles that are “locked in” when in solid form…in” when in solid form…

BUT when they are melted or dissolved in BUT when they are melted or dissolved in water, BOY CAN THEY MOVE!water, BOY CAN THEY MOVE!

Interparticle Forces in Covalent Interparticle Forces in Covalent CompoundsCompounds

Molecules are attracted weakly to one Molecules are attracted weakly to one anotheranother

This makes covalent compoundsThis makes covalent compounds Liquids/gases (almost always!)Liquids/gases (almost always!) Have low MP/BPHave low MP/BP

In addition, Covalent compounds are In addition, Covalent compounds are Not soluble in water (or very slightly)Not soluble in water (or very slightly) poor conductors-WHY??? Think-Pair-Share!!!poor conductors-WHY??? Think-Pair-Share!!!

Why covalent compounds are lousy Why covalent compounds are lousy conductors.conductors.

In order for something to be a conductor, it In order for something to be a conductor, it must have freely-moving charged particles.must have freely-moving charged particles.

Molecules carry little to no charge. Molecules carry little to no charge. Therefore, they cannot conduct electricity Therefore, they cannot conduct electricity well. TOO BAD!well. TOO BAD!

Types of Covalent BondsTypes of Covalent Bonds

Single Bond- When a pair of electrons is Single Bond- When a pair of electrons is sharedshared

Double Bond….you tell me!Double Bond….you tell me! Triple Bond…Triple Bond…