Ionic Compounds:Bonding

Nomenclature

Edward Wen

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Bonding TheoriesBonding: the way atoms attach to make molecules• How and Why atoms attach together in the

manner they do is central to chemistry

An understanding of bonding would: 1) Predict the composition of compounds2) predict the shapes of molecules and properties

of substances 3) design and build molecules with particular sets

of chemical and physical properties, for such as drug design in pharmaceutical industries.

3

Lewis Bonding Theory• Atoms bond with each other because

bonding results in a more stable Electron Configuration

• by either transferring or sharing electrons so that all atoms obtain an Outer Shell with 8electrons (like Noble gases)

Octet RuleSome exceptions: H, He, Li, Be.How to remember? Everyone wants to have an electron configuration like a Noble Gas

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Lewis Symbols of Atomsalso Electron Dot Symbols• Symbol of element : Nucleus and Inner electrons• Dots: around the Symbol as Valence electrons

put one electron on each side first, then pairelements in the same group have the same number of valence electrons same Lewis dot symbols

Na Mg Al Si P S Cl Ar

Be B C N O F NeLi

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Everyone Atom Want to Be Like a Noble Gas!

• Alkali Metals (valence electron ns1) as a group are the most reactive metals

they react with many things and do so rapidly

• Halogens (valence electron ns2np5) are the most reactive group of nonmetals

• one reason for their high reactivity: they are only ONE electron away from having a very stable electron configuration

the same as a noble gas

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Stable Electron ConfigurationAnd Ion Charge

Metals: Cationsby losing enough electrons

to get the same electron configuration as the previous noble gas

Nonmetals: Anionsby gaining enough

electrons to get the same electron configuration as the next noble gas

Atom Atom’s Electron Config

Ion Ion’s ElectronConfig

Na [Ne]3s1 Na+ [Ne]

Mg [Ne]3s2 Mg2+ [Ne]

Al [Ne]3s23p1 Al3+ [Ne]

O [He]2s2p4 O2- [Ne]

F [He]2s22p5 F- [Ne]

P [Ne] 3s23p3 P3- [Ar]

7

Ionic BondsBonding : Metal + Nonmetal• Metal loses electrons to form cation• Nonmetal gains electrons to form anion

Ionic bond results from + & - attraction (Coulombic force)

larger charge = stronger attractionsmaller ion = stronger attraction

• Lewis Theory allow us to predict the correct formulas of ionic compounds

8

Lewis Symbols of Ions• Cations (Cn+) have no valence electrons

Lost in the cation formation

• Anions (An-): 8 valence electronsElectrons gained in the formation of the anion

Li• Li+ + 1e-

:F: + 1e- [:F:]-••• ••

••

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Chemical FormulaChemical formula: describe the compound by

describing the number and type of each atom in the simplest unit of the compound

molecules or ions (Table salt: Cl+, Na-)• Element represented by its letter symbol: H instead

of hydrogen; Na instead of Sodium• #Atoms of each element: the right of the element as a

subscript, H2O (unless if there is only one atom, the 1 subscript is not written)

• Polyatomic groups (multiple atoms in group, example: CO3) are placed in parentheses if more than one

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Ionic CompoundsIons: Metals (Cation Mx+)

and Nonmetals (Anion Ny-)

• No individual molecules!!• have a 3-dimensional

array of cations and anions made of formula units: NaCl, MgO

• Na+ Cl- Na+ Cl- Na+ Cl-

• Cl- Na+ Cl- Na+ Cl- Na+

• Na+ Cl- Na+ Cl- Na+ Cl-

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Ionic Compounds• Name: first Cation, followed by Anion

example: NaCl Sodium ChlorideCation:

Fixed charge vs. Variable charge Polyatomic ion: ammonium NH4

+

Anion:Nonmetal: Chloride Cl-, Oxide O2-

Polyatomic ion: SO42- , OH- , NO3

-

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Physical Properties of Ionic Compounds

Strong Coulombic attraction between the cationsand anions (M+ → ←X-)

• High melting points and high boiling points, thus mostly as Solid state in room temperature.

• Many dissolves well in water and conduct electricity. Water molecule is polar (Hδ+-Oδ--Hδ+) so it can attract both cation and anion.

13

Metal Cations with Fixed Charge

Groups IA, IIA, AZAonly have one possible charge

Groups IA, IIA, Ag+, Zn2+, Al3+

Charge by position on the Periodic Table

IA = +1, IIA = +2, Ag+ (IB), Zn2+(IIB) Al3+(IIIA)

Name is the same as the elementAg+ : silver ionCa2+: calcium ion

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Metal Cations with Variable ChargesCommon Examples: Fe2+/3+, Cu+/2+, Cr3+/6+,

Mn2+/4+, Mn2+/4+, Pb2+/4+, Sn2+/4+, etc )Determine charge by charge on anionName with Roman numeral to indicate charge

Cu+: copper(I) ion Pb4+: lead(IV) ionOr use common name (lower charge “–ous”, higher charge “–ic”)

Cu+: cuprous Cu2+: cupricFe2+: ferrous Fe3+: ferricSn2+: stannous Sn4+: stannic

Metal Cations: Remember the fixed charge cations!

AgZn

Al

= Variable charge

= Fixed charge

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Monatomic Nonmetal Anion (An-)• How much is the charge? the position on the

Periodic Table• Name of the anion: change ending on the

element name to –ide4A = -4 5A = -3 6A = -2 7A = -1

C4- = carbide N3- = nitride O2- = oxide F- = fluoride

Si4- = silicide P3- = phosphide S2- = sulfide Cl- = chloride

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Net charge of Ionic Compound= 0

Net charge = Positive charge from Cation(s) + Negative charge from Anion(s) = 0

• Example: Compound Al2S3, the Net charge = 2 x (+3) + 3 x (-2) = +6 - 6 = 0

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Name of Ionic CompoundsCation:

Fixed charge cation: Na+ => SodiumVariable charge cation = metal name(charge):

Fe3+ => Iron(III)Or use Common Name: Fe3+ => Ferric

Polyatomic ion : NH4+ => Ammonium

Anion:Nonmetal anion: -ide, O2- => oxidePolyatomic ion: SO4

2- => Sulfate

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Example – Naming CsF1. Classify the compound as ionic or

covalent2. For ionic: metal ions as fixed charge or

variable charge?3. Fixed charge metal cation: Name

accordingly.cesium fluoride

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Variable charge metal comopound

Metal listed first in formula & name

1. Metal cation Nonmetal anion2. metal cation Metal(Roman Numeral): to indicate

its charge. Iron(II), Copper(I) determine charge from anion chargeAlternatively, use common name

3. Nonmetal anion Nonmetal name ended with –ide: Chloride, Oxide

Example: Iron(II) chloride, Copper(I) oxide

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How to find the charge on metal ions with variable charge?

• Example: Name Compound Fe2O3Since the sum of all charges equals zero, the charge

on iron ions are unknown and oxide ion has –2 charge, then we have

2 x Fe + 3 x (-2) = 0 Fe = +3, each iron ion has a charge of +3Name: iron(III) oxideKey: knowing the charge on ANIONs!

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Example: Naming variable charge metal compound Fe2O3

1. Identify the compound as ionic or covalent

2. Identify the metal ion as fixed charge or variable charge.

3. Find the charge of metal ion using the charge on the known anion

Note: What is the name and charge of anion O?4. Name accordingly.Iron(III) oxide Or Ferric chloride

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Practice: Naming Ionic compounds

• HgF2

• CuI2

• Cr2S3

• SnCl4

• Mg3N2

• Hg2Cl2

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Naming Ionic compounds Hints: find type II ion charge from anion

• HgF2 : Two F- = -2• CuI2 : Two I- = -2• CaCl2 : both fixed charges• Cr2O3 : Three O2- = -6• SnBr4 : Four Br- = -4• Mg3N2 : both fixed charges• Ag2S : both fixed charges

• HgF2 : Two F- = -2 Hg = +2• CuI2 : Two I- = -2Cu = +2• CaCl2 : both fixed charges• Cr2O3 : Three O2- = -6 Cr = +3• SnBr4 : Four Br- = -4 Sn = +4• Mg3N2 : both fixed charges• Ag2S : both fixed charges

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Answer key: names of ionic compounds

• HgF2 = Mercury(II) fluoride• CuI2 = copper(II) iodide• CaCl2 = calcium chloride• Cr2O3 = chromium(III) oxide• SnBr4 = tin(IV) bromide• Mg3N2 = magnesium nitride• Ag2S = silver sulfide

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Polyatomic Ions

Mg(NO3)2

compound calledmagnesium nitrate

symbol of the polyatomic ion called nitrate

symbol of the polyatomic ion called sulfate

CaSO4

compound calledcalcium sulfate

implied “1” subscripton magnesium

implied “1” subscripton calcium

parentheses to group two NO3’s no parentheses for one SO4

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Polyatomic Ions:Nitrate NO3

-, Sulfate SO42-

Mg(NO3)2

compound calledmagnesium nitrate

CaSO4

compound calledcalcium sulfate

subscript indicatingtwo NO3 groups

no subscript indicatingone SO4 group

implied “1” subscripton nitrogen, total 2 N

implied “1” subscripton sulfur, total 1 S

stated “3” subscripton oxygen, total 6 O

stated “4” subscripton oxygen, total 4 O

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Polyatomic Anions: -ATE ions

CO32-

carbonateNO3

-

nitrate

SiO32-

silicatePO4

3-

phosphateSO4

2-

sulfateClO3

-

chlorate

AsO43-

arsenateSeO4

2-

selenateBrO3

-

bromate

IO3-

iodate

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Periodic Pattern of Polyatomic Ions-ate groups

BO33- NO3

-

SiO32- PO4

3- SO42- ClO3

-

AsO43- SeO4

2- BrO3-

TeO42- IO3

-

CO32-

IIIA IVA VA VIA VIIA

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Patterns for Polyatomic Ions1. elements in the same Group form similar

polyatomic ionssame number of O’s and same charge

ClO3- = chlorate (-1 charge)

BrO3- = bromate (-1 charge)

2. if the polyatomic ion starts with H, the name adds hydrogen- prefix before name and add 1 to the charge

CO32- = carbonate ∴ HCO3

-1 = hydrogen carbonate

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Patterns for Polyatomic Ions-ate ion

chlorate = ClO3-

• -ate ion + 1 O ⇒ same charge, per- prefixperchlorate = ClO4

-

• -ate ion – 1 O ⇒ same charge, -ite suffixchlorite = ClO2

-

• -ate ion – 2 O ⇒ same charge, hypo- prefix, -ite suffix

hypochlorite = ClO-

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Polyatomic Anions: -ite, hypo- -ite, (-ate), per- -ate

ClO-

hypochlorite

NO2-

nitritePO3

3-

phosphiteSO3

2-

sulfiteClO2

-

chlorite

NO3-

nitratePO4

3-

phosphateSO4

2-

sulfateClO3

-

chlorate

ClO4-

perchlorate

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-ATE/-ITE ions in Our Lives

ClO-

(bleach)

NO2-

(preserve meat)

PO33-

(plant medicine)

SO32-

(wine, oxygen buster)

ClO2-

(bleach, disinfect)

NO3-

(fertilizer, explosives)

PO43-

(bone/teeth, fertilizer, soda)

SO42-

(plaster, car battery, sea salt)

ClO3-

(older pyrotechnics)

ClO4-

(pyrotechnics, solid fuel rocket)

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Polyatomic Ions to RememberName Formula

acetate C2H3O2–

carbonate CO32–

hydrogen carbonate(aka Bicarbonate) HCO3

–

hydroxide OH–

nitrate NO3–

nitrite NO2–

permanganate MnO4–

chromate CrO42–

dichromate Cr2O72–

ammonium NH4+

Name Formula

hypochlorite ClO–

chlorite ClO2–

chlorate ClO3–

perchlorate ClO4–

sulfate SO42–

Hydrogen sulfate(aka Bisulfate)

HSO4–

sulfite SO32–

Hydrogen sulfite(aka Bisulfite) HSO3

–

cyanide CN–

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Polyatomic Ions in Our LivesC2H3O2

– In vinegar as acetic acid

CO32– Soda drink

HCO3– Baking soda, baking power, acid spill

neutralizer

OH– In liquid plumber/Drano as NaOH

MnO4– Disinfectant, “aging” for movie making

CrO42– Chrome plating (faucet, etc.)

CN– Highly Poisonous; Plant seeds; blue pigment

NH4+ Fertilizer; metabolic waste from animals

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Other Polyatomic Ions in Our Lives

ClO-

(bleach)

NO2-

(preserve meat)

PO33-

(plant medicine)

SO32-

(wine, oxygen buster)

ClO2-

(bleach, disinfect)

NO3-

(fertilizer, explosives)

PO43-

(bone/teeth, fertilizer, soda)

SO42-

(plaster, car battery, sea salt)

ClO3-

(older pyrotechnics)

ClO4-

(pyrotechnics, solid fuel rocket)

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Compounds Containing Polyatomic Ions

• Fixed charge metal cation + Polyatomic ion: NaNO3

• Variable charge metal cation + Polyatomic ion: CuSO4

• Polyatomic cation + Nonmetal ion (-ide): NH4Cl• Polyatomic cation + Polyatomic ion: (NH4)2SO4

Important!: If, and only if, more than ONE polyatomic ions are present in a formula, use parenthesis and subscript to indicate the number of polyatomic ions

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Example – Naming Ionic with Polyatomic IonNa2SO4

1. Ionic or covalent compound?2. Ionic: fixed charge or variable charge metal cation?3. fixed charge metal cation: Name accordingly.

Sodium sulfate

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Example – Naming Ionic with Polyatomic IonFe(NO3)3

1. Ionic or covalent compound?2. Ionic: fixed charge or variable charge metal cation?3. Variable charge metal cation: determine the charge

based on the charge of anionNote: what is the name and charge on NO3?

4. Name accordingly.

Iron(III) nitrate

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Practice: Naming Ionic compounds

• Hg2SO4

• CuClO3

• Zn(NO3)2

• FeCO3

• Sn(SO3)2

• CoPO4

• Al(ClO4)3

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Hints: Naming Ionic compounds

• Hg2SO4 : charge of sulfate = -1• CuClO3 : charge of chlorate = -1• Zn(NO3)2 charge of nitrate = -1• FeCO3 : charge of carbonate = -2• Sn(SO3)2: charge of sulfite = -1• CoPO4 : charge of phosphate = -3• Al(ClO4)3 : charge of perchlorate = -1

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Keys: Naming Ionic compounds

• Hg2SO4 : mercury(I) sulfate• CuClO3 : copper(I) chlorate• Zn(NO3)2 zinc nitrate• FeCO3 : iron(II) carbonate• Sn(SO3)2: tin(IV) sulfite• CoPO4 : cobalt(III) phophate• Al(ClO4)3 : aluminum perchlorate

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Review: Naming Compounds

• CuSO3 copper(II) sulfite• AgClO silver hypochlorite• Al2S3 aluminum sulfide• FeI2 iron(II) iodide• Sn(NO3)4 tin(IV) nitrate• Ba3(PO4)2 barium phosphate • (NH4)2S ammonium sulfide

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Write Chemical Formula using the charge of known ions

• Example: Compound between Ca2+ and PO4

3- , the number of ions of each needs to be 3 and 2, so that the combined charge = 3 x (+2) + 2 x (-3) = 0

Therefore the formula for the compound is Ca3(PO4)2

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Write Chemical Formula using the charge of known ions

“Criss-Cross-Simplify”:• The charge of an ion turns into the subscript (the

number) of the counterpart ionPb4+ O2- Pb2O4

• Since the subscripts in an ionic compound represents the RATIO among the ions, the subscripts need to be simplified when there is common denominator

Pb2O4 PbO2

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Key for Writing formulas (I): use criss-cross-reduce

• copper(II) chloride CuCl2• aluminum oxide Al2O3• magnesium phosphide Mg3P2• iron(II) bromide FeBr2• lead(II) sulfide FeS• zinc iodide ZnI2• sodium nitride Na3N

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Practice: Write Chemical Formulae

• Chromium(II) Chloride • Cesium phosphate• Lead(II) oxide• Zinc nitrate• Iron(III) sulfite• Strontium nitride• Ammonium carbonate

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Key: Write Chemical Formulae

• Chromium(II) Chloride • Cesium phosphate• Lead(II) oxide• Zinc nitrate• Iron(III) sulfite• Strontium nitride• Ammonium carbonate

CrCl2Cs3PO4PbOZn(NO3)2Fe3(SO3)2Sr3N2(NH4)2CO3

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Key: Writing formulas (I)

• copper(I) sulfate: Cu2SO4• aluminum chlorate: Al(ClO3)3• magnesium phosphate: Mg3(PO4)2• iron(II) carbonate : FeCO3• lead(II) acetate: Pb(C2H3O2)2• zinc sulfite : ZnSO3• sodium nitrite: NaNO2• Nitrogen gas: N2

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More on Writing formulae

• copper(II) sulfate• aluminum perchlorate• hydroiodic acid• iron(III) bromide• Diphosphorus pentoxide• lead(IV) nitride• zinc carbonate • helium gas

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Key: Writing formulae

• copper(II) sulfate CuSO4• aluminum perchlorate Al(ClO4)3• hydroiodic acid HI• iron(III) bromide FeBr3• Diphosphorus pentoxide P2O5• lead(IV) nitride Pb3N4• zinc carbonate ZnCO3• ammonium nitrite NH4NO2• helium gas He