Ionic Bonding

Ionic Bonding

q Students know atoms combine toform molecules by sharing electrons toform covalent or metallic bonds or byexchanging electrons to form ionicbonds.q Students know salt crystals, suchas NaCl, are repeating patterns ofpositive and negative ions heldtogether by electrostatic attraction.

Bondsq Forces that hold groups of atomstogether and make them functionas a unit.v Ionic bonds – transfer ofelectronsv Covalent bonds – sharing ofelectrons

Ionic Bonding:The Formation of Sodium Chlorideq Sodium has 1 valence electronq Chlorine has 7 valence electronsq An electron transferred giveseach an octetNa: 1s 2 2s 2 2p 6 3s 1Cl: 1s 2 2s 2 2p 6 3s 2 3p 5

Ionic Bonding:The Formation of Sodium ChlorideThis transfer forms ions, eachwith an octet:Na + 1s 2 2s 2 2p 6Cl - 1s 2 2s 2 2p 6 3s 2 3p 6

Ionic Bonding:The Formation of Sodium ChlorideThe resulting ions come togetherdue to electrostatic attraction(opposites attract):Na + Cl -The net charge on the compoundmust equal zero

Ionic BondsMetal to NonmetalHigh ENDMetal forms cationNonmetal forms anion

MetalMonatomicCationsIon nameLithium Li + LithiumSodium Na + SodiumPotassium K + PotassiumMagnesium Mg 2+ MagnesiumCalcium Ca 2+ CalciumBarium Ba 2+ BariumAluminum Al 3+ Aluminum

NonmetalMonatomicAnionsIon NameFluorine F - FluorideChlorine Cl - ChlorideBromine Br - BromideIodine I - IodideOxygen O 2- OxideSulfur S 2- SulfideNitrogen N 3- NitridePhosphorus P 3- Phosphide

Sodium Chloride Crystal LatticeIonic compounds formsolid crystals at ordinarytemperatures.Ionic compounds organizein a characteristiccrystal lattice ofalternating positive andnegative ions.All salts are ionic compounds and form crystals.

Ionic solids are brittleStrong repulsion breaks crystal apart.Force+ - + -+ - + -- + - ++ - + -- + - +

Characteristics of Ion Bonding in a Crystal LatticeVisual Concept

Properties of Ionic CompoundsStructure:Crystalline solidsMelting point: Generally highBoiling Point:ElectricalConductivity:Solubility inwater:Generally highExcellent conductors,molten and aqueousGenerally soluble

Lattice Energy- the ionic bond---the energy released when thecrystal lattice formation is formed---Lattice energies are listed as negativevalues to indicate that energy is given offwhen ions come together to form the ioniccrystal.The greater the latticeenergy… the stronger the ionicbonding!

VocabularyCOMPOUND2 elementsbinarycompoundNaClmore than 2elementsternarycompoundNaNO 3

VocabularyION1 atom 2 or more atomsmonatomicIonNa +polyatomicIonNO 3-

lithium atomLilithium ione - Li +e -e -3p +loss ofone valenceelectrone - 3p +e -e -fluorine atomFe -e -e - e -e -e - e - e -9p +e - gain ofone valenceelectrone -e - e -fluoride ionF 1-e - e -9p +e - e -e -e - e -

Formation of Cationlithium atomLilithium ionLi +e - e -e -3p +loss ofone valenceelectrone - 3p +e -

Formation of Anionfluorine atomFfluoride ionF 1-e -e -e -gain ofe - one valenceelectrone - 9p +e -e -e - e - e -e -e - e -e - e -9p +e - e -e -e - e -

Formation of Ionic Bondlithium ionLi +fluoride ionF 1-e -e - e -e - 3p +e -e - e -9p +e - e -e -e - e -

Ionic bonding: Li + Cl1e -3p +4n 0 2e- 1e -7e - 8e - 2e - 17p+ 18n03p +4n 02e - 8e - 8e - 2e 17p +18n 0lithium atom chlorine atom lithium ion chloride ionLi Cl [Li] + [ Cl ]–

Ionic bonding: Li + CIonic compound formation equationLi + Cl → [Li] + [ Cl ] –

Ionic bonding: Mg + OMgO[Mg] 2+ [ O] 2–1e -12p +12n 02e - 8e - 2e -6e - 2e - 8p +8n012p +12n 02e - 8e -8e - 2e - 8p +8n01e -

Lewis DotDiagrams andBONDING (Ionic )

How do we show the valence electrons fordifferent elements?* dot diagrams were developedby American, G.N. Lewis, inthe 1920's* they are called Lewisstructure or Lewis dotdiagrams

Electron-Dot NotationTo keep track of valenceelectrons, it is helpful touse electron-dotnotation.Electron-dot notationshows only the valenceelectrons of an atom ofa particular element,indicated by dots placedaround the elementssymbol. The inner-shellelectrons are notshown.

Electron-Dot NotationClick below to watch the Visual Concept.Visual Concept

Hydrogen has one valence electronNitrogen has five valenceelectrons.

Write the electron dotdiagram for• Na• Mg• C• O• F• Ne• He1s 2 2s 2 2p 6 3s 11s 2 2s 2 2p 6 3s 21s 2 2s 2 2p 21s 2 2s 2 2p 41s 2 2s 2 2p 51s 2 2s 2 2p 61s 2NaNeMgHeCOF

Ionic Bondingtransfer of electronNa+1 -1ClNaCl

Ionic Bonding• All the electrons must be accountedfor!Ca +2 +2PP -3Ca-3Ca +2

Ionic BondingCa 2+ Ca P P 3-Ca 2+ 3 2Formula UnitCa 2+ P 3-Ca 2+Ca 2+Ca 2+P 3-P 3-

Ionic Formation EquationCa+ P3[Ca] +2 2[ P ] –3

* monatomic ions can bewritten with dot diagrams* as before, dots are used todemonstrate e-* symbol is in [brackets] torepresent ions* charge is placed on theupper right corner

Do the dot diagrams forNa, Mg, Al, P, S, Cl ions

+1-1

PracticeDraw the Lewis Dot Diagrams forthe following compounds:1. Lithium iodide2. Calcium chloride3. Potassium oxideExample: Magnesium Chloride[Mg] +2 2[ Cl ] -1

Polyatomic IonsAn example of a polyatomic ion is the ammonium ion:. It is sometimes written as toNH++4[NH ]show that the group of atoms as a whole has a charge of+1.The charge of the ammonium ion is determined asfollows:seven protons in the nitrogen atomplus the four protons in the four hydrogen atomsgive the ammonium ion a total positive charge of+11.4

When nitrogen and hydrogenatoms combine to form anammonium ion, one of theirelectrons is lost, giving thepolyatomic ion a total negativecharge of -10.The total charge is therefore(+11) + (-10) = +1.

Some examples of Lewis structures of polyatomicions are shown below.