Chapter 4: Chapter 4: Chemical BondingChemical Bonding

When Atoms CollideWhen Atoms Collide

Unit ObjectivesUnit 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.

• Explain how interparticle forces affect the Explain how interparticle forces affect the properties of ionic & covalent compounds.properties of ionic & covalent compounds.

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 burning

2H2 + O2 2H2O

sodium metal & chlorine

Na + Cl NaCl

sodium iodide & mercury (II) chloride

2NaI + HgCl2 2NaCl + HgI2

The Noble GasesThe Noble Gases

All of them occur in natureAll of them occur in nature BUT no compounds containing them ever BUT no compounds containing them ever

found in nature found in nature Analysis: they are unreactive/stable as they Analysis: they are unreactive/stable as they

areare Question: Why are they so stable?Question: Why are they so stable? Data: When we look at their electron Data: When we look at their electron

configurations, they all* have 8 valence e-s! configurations, they all* have 8 valence e-s! (*except He)(*except He)

The Noble Gases (cont.)The Noble Gases (cont.)

Something about having 8 Something about having 8 valence e-s (or 2, if you are a valence e-s (or 2, if you are a small atom) makes you small atom) makes you stable, “Happy”stable, “Happy”

Called “Noble Gas ConfigurationCalled “Noble Gas Configuration””

Atoms can Get NGC in one of 2 Atoms can Get NGC in one of 2 ways (cont.)ways (cont.)

1. Share e-s (COVALENT bond)1. Share e-s (COVALENT bond)This occurs when the 2 atoms in This occurs when the 2 atoms in

the bond pull on their e-s w/the the bond pull on their e-s w/the same (or similar) strengthsame (or similar) strength

Typically occurs between 2 Typically occurs between 2 ___________.___________.

Atoms can Get NGC in one of 2 Atoms can Get NGC in one of 2 ways (cont.)ways (cont.)

2. Lose/gain e-s (IONIC bond)2. Lose/gain e-s (IONIC bond)This occurs when the 2 atoms This occurs when the 2 atoms in the bond pull on their e-s in the bond pull on their e-s w/different strengthsw/different strengths

Typically occurs btwn a Typically occurs btwn a _____ & a _____._____ & a _____.

3 “Classes” of Elements3 “Classes” of Elements Metals =Metals = pinkpink

Conductors? Conductors? Yes!Yes!

Hold e-s? Hold e-s? LooselyLoosely

How many V.E’s? How many V.E’s? 1-31-3

Nonmetals =Nonmetals = greengreen

Conductors? Conductors? No!No!

Hold e-s? Hold e-s? TightlyTightly

How many V.E.’s? How many V.E.’s? 5-75-7

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

Ions & the Octet RuleIons & the Octet Rule

Ions are charged particles that have lost or Ions are charged particles that have lost or gained e-s to satisfy the octet rule (8 e-s)gained e-s to satisfy the octet rule (8 e-s)

They will typically form based on what They will typically form based on what requires the smallest gain or loss of e-s to requires the smallest gain or loss of e-s to complete an octet.complete an octet.

Formation of an ionic bondFormation of an ionic bond When e-s are lost by 1 atom & gained When e-s are lost by 1 atom & gained

by another, one atom develops a + by another, one atom develops a + charge (“cation”) and the other charge (“cation”) and the other develops a – charge (anion)develops a – charge (anion)

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

Note: you will not always have a 1:1 Note: you will not always have a 1:1 ratio of + to - ions.ratio of + to - ions. Ex: MgIEx: MgI2 2 -see next slide -see next slide

Formation of MgI2Formation of MgI2

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

.. .. ..

.. .. .. ...Mg. + :I: :I: → Mg2+ + :I: - :I:-

. . .. ..

ACTIVITY: Egg Carton AtomsACTIVITY: Egg Carton AtomsIonic BondingIonic Bonding

MATERIALSMATERIALSEgg 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-One will donate e-s & one will receive e-s.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 How many e-s must be

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

gained (Which is easier?)gained (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! Partner 1: 3 e-sPartner 1: 3 e-s Partner 2: 9 e-sPartner 2: 9 e-s

(Identify your elements first.)(Identify your elements first.) With your new set of “electrons,” form an ionic compound with your partner.With your new set of “electrons,” form an ionic compound with 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 & FResults of Example 2: Li & FDATA 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

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 e- configurationsame e- 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 Tell us:Tell us:

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

The smallest unit of an Ionic Compound is called a The smallest unit of an Ionic Compound is called a ““Formula UnitFormula Unit” ”

The smallest unit of a Covalent compound is called a The smallest unit of a Covalent compound is called a Formula Unit Formula Unit or or “Molecule“Molecule” ”

To Explain Why…To Explain Why…

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

You never have just 1 Na and 1 Cl, You never have just 1 Na and 1 Cl, for examplefor example

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

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

Each ion is “locked in” in Each ion is “locked in” in 6 directions (ex: each Na+ 6 directions (ex: each Na+ is surrounded by 6 Cl-)is surrounded by 6 Cl-)

Giant Ionic LatticeGiant Ionic Lattice

Rotating NaCl LatticeRotating NaCl Lattice

e Fig 22-25 p 570

Properties of Ionic CompoundsProperties of Ionic Compounds

BrittleBrittleCubic in shapeCubic in shapeVery stableVery stableSolids (high MP, BP.)Solids (high MP, BP.)Very soluble in waterVery soluble in waterElectrolyteElectrolyte

Ionic Compounds-ElectrolytesIonic Compounds-Electrolytes 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 Ions are charged particles that are “locked in” when in solid form…“locked in” when in solid form…

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

Interparticle Forces Interparticle Forces The attraction between formula units The attraction between formula units

(particles of a substance) is called: (particles of a substance) is called: “INTERPARTICLE FORCES”“INTERPARTICLE FORCES”

strong IP forces between adjacent NaCl strong IP forces between adjacent NaCl units, for example.units, for example.

weak attraction between adjacent weak attraction between adjacent molecules of covalent compounds, H2O, molecules of covalent compounds, H2O, for example.for example.

Interparticle Forces in Covalent Interparticle Forces in Covalent CompoundsCompounds

Molecules have little to no charge Molecules have little to no charge so they are attracted v. weakly to so they are attracted v. weakly to one anotherone another

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

Interparticle Forces in Covalent Interparticle Forces in Covalent Compounds, cont.Compounds, cont.

Not soluble in water (or very Not soluble in water (or very slightly) ex: oil, gas, CO2slightly) ex: oil, gas, CO2

poor conductors-WHY??? poor conductors-WHY??? Think-Pair-Share!!!Think-Pair-Share!!!

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

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

Types of Covalent BondsTypes of Covalent Bonds

Single Bond- When a pair Single Bond- When a pair of electrons is sharedof electrons is shared

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

Triple Bond…Triple Bond…

Examples of Covalent Examples of Covalent CompoundsCompounds

The properties of covalent The properties of covalent compounds vary more widely than compounds vary more widely than those of ionic cpds.those of ionic cpds.

Ex: butter, water, CO2, gasoline, Ex: butter, water, CO2, gasoline, candle wax, table sugar, alcoholcandle wax, table sugar, alcohol

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.