Bonding Between Atoms

Bonding Between AtomsBonding Between Atoms

Why do Atoms Form Bonds?Why do Atoms Form Bonds?To get a To get a stable octetstable octet of valence electrons. of valence electrons.

Called a “noble gas configuration”Called a “noble gas configuration”

IONIC BOND = valence e- transferred

COVALENT BOND = valence e- shared

Changes in EnergyChanges in Energy

Energy is Energy is releasedreleased when bonds form. when bonds form. (exothermic)(exothermic)

Results in lower energy, more stabilityResults in lower energy, more stabilityKnow example…Know example…

Lewis Dot Diagrams of AtomsLewis Dot Diagrams of Atoms

Show valence electrons that are involved Show valence electrons that are involved in bondingin bonding

Lewis Dot Diagrams of IonsLewis Dot Diagrams of Ions

Positive Ions (cations): lose outer shell Positive Ions (cations): lose outer shell valence to get stable octet.valence to get stable octet.

Negative Ions (anions): gain electrons to Negative Ions (anions): gain electrons to complete outer shell octet.complete outer shell octet.

Ionic BondingIonic Bonding

Happens between metals Happens between metals and nonmetalsand nonmetals

Atoms Atoms Become IonsBecome Ions

Metals Lose Electrons:Metals Lose Electrons: become (+) ion become (+) ion

Ex: Mg is 2-8-2Ex: Mg is 2-8-2Loses 2 electrons to become MgLoses 2 electrons to become Mg+2+2 2-82-8

Nonmetals Gain ElectronsNonmetals Gain Electrons: : usually take top (-) chargeusually take top (-) charge

become (–) ion become (–) ion Ex: Cl is 2-8-7Ex: Cl is 2-8-7Gains 1 electron to become ClGains 1 electron to become Cl-1-1 2-8-82-8-8

Electron TransferElectron Transfer

As ions form, an exchange or As ions form, an exchange or transfertransfer of of electrons happens.electrons happens.

Lithium (metal) 2-1 Fluorine (nonmetal) 2-7

Electronegativity DifferenceElectronegativity Difference

Atoms in ionic compounds Atoms in ionic compounds

have have large differences in their EN large differences in their EN values ( > 1.7)values ( > 1.7)

The greater the EN difference, theThe greater the EN difference, the

more more “Ionic Character”.“Ionic Character”.

Ex: Ex: EN ValuesEN ValuesMetalMetal Na = 0.9Na = 0.9Nonmetal Nonmetal Cl = 3.2Cl = 3.2

Nonmetal with higher EN Nonmetal with higher EN “takes” electron(s) from metal“takes” electron(s) from metal

Positively and negatively charged ions form and Positively and negatively charged ions form and attract each other due to OPPOSITE CHARGES.attract each other due to OPPOSITE CHARGES.

Attraction forms an Attraction forms an

IONIC BONDIONIC BOND

Forming Table Salt :6 minutesForming Table Salt :6 minutes http://science360.gov/obj/video/c8b6ed58-5791-4fc1-8619-62fd8d99d9d0/atoms-bond-ionic-bondshttp://science360.gov/obj/video/c8b6ed58-5791-4fc1-8619-62fd8d99d9d0/atoms-bond-ionic-bonds

+ ion

- ion

Ionic compounds have a Ionic compounds have a uniform crystalline uniform crystalline lattice structure.lattice structure.

https://www.youtube.com/watch?v=lhC42qxk5kQ&safe=active

Can you identify an ionic compound from a Can you identify an ionic compound from a covalent?covalent?

MgBrMgBr22

Ca(NOCa(NO33))22

PP22OO55

COCO22

NaNa22SS

HH2200

Drawing Lewis Dot Drawing Lewis Dot Diagrams of Ionic Diagrams of Ionic Compounds Compounds

Do Page 7 in Do Page 7 in Bonding PacketBonding Packet

Writing Ionic FormulasWriting Ionic Formulas

Ionic Compounds are NeutralIonic Compounds are Neutral

Subscripts showSubscripts show

ratio of ions ratio of ions

Total positive andTotal positive and

negative chargesnegative charges

must balancemust balance so the so the

compound iscompound is

electrically neutral.electrically neutral.

Writing Neutral Ionic FormulasWriting Neutral Ionic Formulas Write symbols of elementsWrite symbols of elements Write the chargesWrite the charges Criss-Cross charges Criss-Cross charges if necessaryif necessary to balance the to balance the

formulaformula Put parenthesis around polyatomic ions if more than Put parenthesis around polyatomic ions if more than

one in formulaone in formula

Simplify if needed.Simplify if needed.

Tutorial on writing ionic formulas 9 minhttp://www.youtube.com/watch?v=vscoYh6m46M

Stock System for Naming Stock System for Naming Ionic CompoundsIonic Compounds

Binary:Binary:

Contain ions of 2 Contain ions of 2 elements elements

Ex:Ex: MgClMgCl22, Al, Al22OO33, ,

NaClNaCl

Naming Binary IonicsNaming Binary IonicsName metalName metalName nonmetal with “-ide” ending.Name nonmetal with “-ide” ending.

Ex: NaCl, MgBrEx: NaCl, MgBr22, CaO, Al, CaO, Al22SS33

Ternary:Ternary: Contain 3 elements Contain 3 elementsPolyatomic ionPolyatomic ion present. present.Elements inside the polyatomic ion are Elements inside the polyatomic ion are

covalently bonded (all nonmetals).covalently bonded (all nonmetals).

Thus these compounds Thus these compounds contain both ionic contain both ionic and covalent bondsand covalent bonds!!!!

Ex:Ex: NaNONaNO33, Ca, Ca33(PO(PO44))2, 2, NHNH44ClCl

Naming Ternary Ionics (with polyatomic)Naming Ternary Ionics (with polyatomic)Name MetalName MetalName polyatomic ionName polyatomic ion If two polyatomics, name them bothIf two polyatomics, name them both

When to Use a Roman NumeralWhen to Use a Roman Numeral

Roman numerals are used when the Roman numerals are used when the metalmetal can have more than one possible charge.can have more than one possible charge.

Roman numeral indicates the charge the Roman numeral indicates the charge the metal takes in that compound and metal takes in that compound and must be must be indicated in the nameindicated in the name

Ex:Ex: NiBrNiBr22 Nickel II BromideNickel II Bromide

NiBrNiBr33 Nickel III Bromide Nickel III Bromide

Crash Course Chemistry: NomenclatureCrash Course Chemistry: Nomenclature (only watch first 6 minutes, skip section on naming acids for now)(only watch first 6 minutes, skip section on naming acids for now)

http://www.youtube.com/watch?http://www.youtube.com/watch?v=mlRhLicNo8Qv=mlRhLicNo8Q

Properties of Ionic Properties of Ionic CompoundsCompounds

High Melting PointHigh Melting PointAttraction between theAttraction between theions is very strong.ions is very strong.

Requires a lot of heatRequires a lot of heatenergy to separateenergy to separateions and make solidions and make solidcrystal melt.crystal melt.

Higher MP than covalentsHigher MP than covalents

Solubility in WaterSolubility in Water

Most ionics will Most ionics will dissolve in water, or dissolve in water, or be be ““solublesoluble”.”.

When dissolved in water When dissolved in water they are “aqueous”they are “aqueous”

Ex: NaCl (aq)Ex: NaCl (aq)

Water is a “polar molecule”Water is a “polar molecule”. . Acts like a magnet to pull ions apart and into Acts like a magnet to pull ions apart and into

solution.solution. Ions are now “dissociated” or “hydrated” ions.Ions are now “dissociated” or “hydrated” ions.

http://youtu.be/EBfGcTAJF4ohttp://youtu.be/EBfGcTAJF4o

ConductivityConductivity

Ionic compounds Ionic compounds conduct when ions conduct when ions are are ““mobilemobile”” or free or free to move about.to move about.

ConductivityConductivity Ionic compounds conduct when:Ionic compounds conduct when:

Molten (melted/liquid) Molten (melted/liquid) (l)(l)Aqueous Aqueous (aq)(aq)

Note: They Note: They DO NOT DO NOT conduct conduct when solid as the ions are locked when solid as the ions are locked in place.in place.

Covalent Compounds in water Covalent Compounds in water do not conductdo not conduct

Dancing Queen: Song about Ionic vs Dancing Queen: Song about Ionic vs Covalent BondingCovalent Bonding

http://www.youtube.com/watch?v=QIfTT-http://www.youtube.com/watch?v=QIfTT-_-xLo_-xLo

Crash Course: Atomic Hookups Crash Course: Atomic Hookups http://www.youtube.com/watch?http://www.youtube.com/watch?

v=QXT4OVM4vXIv=QXT4OVM4vXI