Ionic Compounds: Bonding Nomenclature. Edward Wen

Transcription

1 Ionic Compounds: Bonding Nomenclature Edward Wen

2 Bonding Theories Bonding: 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 compounds 2) 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. 2

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 8 electrons (like Noble gases) Octet Rule Some exceptions: H, He, Li, Be. How to remember? Everyone wants to have an electron configuration like a Noble Gas 3

4 Lewis Symbols of Atoms also 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 pair elements in the same group have the same number of valence electrons same Lewis dot symbols Li Be B C N O F Ne Na Mg Al Si P S Cl Ar 4

5 Everyone Atom Want to Be Like a Noble Gas! Alkali Metals (valence electron ns 1 ) as a group are the most reactive metals they react with many things and do so rapidly Halogens (valence electron ns 2 np 5 ) 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 5

6 Stable Electron Configuration And Ion Charge Metals: Cations by losing enough electrons to get the same electron configuration as the previous noble gas Nonmetals: Anions by gaining enough electrons to get the same electron configuration as the next noble gas Atom Atom s Electron Config Ion Ion s Electron Config Na [Ne]3s 1 Na + [Ne] Mg [Ne]3s 2 Mg 2+ [Ne] Al [Ne]3s 2 3p 1 Al 3+ [Ne] O [He]2s2p 4 O 2 [Ne] F [He]2s 2 2p 5 F [Ne] P [Ne] 3s 2 3p 3 P 3 [Ar] 6

7 Ionic Bonds Bonding : Metal + Nonmetal Metal loses electrons to form cation Nonmetal gains electrons to form anion Ionic bond results from + & attraction (Coulombic force) larger charge = stronger attraction smaller ion = stronger attraction Lewis Theory allow us to predict the correct formulas of ionic compounds 7

8 Lewis Symbols of Ions Cations (C n+ ) have no valence electrons Lost in the cation formation Li Li + + 1e Anions (A n ): 8 valence electrons Electrons gained in the formation of the anion :F: + 1e [:F:] 8

9 Chemical Formula Chemical 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, H 2 O (unless if there is only one atom, the 1 subscript is not written) Polyatomic groups (multiple atoms in group, example: CO 3 ) are placed in parentheses if more than one 9

10 Ionic Compounds Ions: Metals (Cation M x+ ) and Nonmetals (Anion N y ) No individual molecules!! have a 3dimensional 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 10

11 Ionic Compounds Name: first Cation, followed by Anion example: NaCl Sodium Chloride Cation: Fixed charge vs. Variable charge Polyatomic ion: ammonium NH 4 + Anion: Nonmetal: Chloride Cl, Oxide O 2 Polyatomic ion: SO 4 2, OH, NO 3 11

12 Physical Properties of Ionic Compounds Strong Coulombic attraction between the cations and 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 (H δ+ O δ H δ+ ) so it can attract both cation and anion. 12

13 Metal Cations with Fixed Charge Groups IA, IIA, AZA only have one possible charge Groups IA, IIA, Ag +, Zn 2+, Al 3+ Charge by position on the Periodic Table IA = +1, IIA = +2, Ag + (IB), Zn 2+ (IIB) Al 3+ (IIIA) Name is the same as the element Ag + : silver ion Ca 2+ : calcium ion 13

14 Metal Cations with Variable Charges Common Examples: Fe 2+/3+, Cu +/2+, Cr 3+/6+, Mn 2+/4+, Mn 2+/4+, Pb 2+/4+, Sn 2+/4+, etc ) Determine charge by charge on anion Name with Roman numeral to indicate charge Cu + : copper(i) ion Pb 4+ : lead(iv) ion Or use common name (lower charge ous, higher charge ic ) Cu + : cuprous Cu 2+ : cupric Fe 2+ : ferrous Fe 3+ : ferric Sn 2+ : stannous Sn 4+ : stannic 14

15 Metal Cations: Remember the fixed charge cations! = Fixed charge = Variable charge Zn Ag Al

16 Monatomic Nonmetal Anion (A n ) How much is the charge? the position on the Periodic Table Name of the anion: change ending on the element name to ide 4A = 4 5A = 3 6A = 2 7A = 1 C 4 = carbide N 3 = nitride O 2 = oxide F = fluoride Si 4 = silicide P 3 = phosphide S 2 = sulfide Cl = chloride 16

17 Net charge of Ionic Compound = 0 Net charge = Positive charge from Cation(s) + Negative charge from Anion(s) = 0 Example: Compound Al 2 S 3, the Net charge = 2 x (+3) + 3 x (2) = +6 6 = 0 17

18 Name of Ionic Compounds Cation: Fixed charge cation: Na + => Sodium Variable charge cation = metal name(charge): Fe 3+ => Iron(III) Or use Common Name: Fe 3+ => Ferric Polyatomic ion : NH 4+ => Ammonium Anion: Nonmetal anion: ide, O 2 => oxide Polyatomic ion: SO 2 4 => Sulfate 18

19 Example Naming CsF 1. Classify the compound as ionic or covalent 2. For ionic: metal ions as fixed charge or variable charge? 3. Fixed charge metal cation: Name accordingly. cesium fluoride 19

20 Variable charge metal comopound Metal listed first in formula & name 1. Metal cation Nonmetal anion 2. metal cation Metal(Roman Numeral): to indicate its charge. Iron(II), Copper(I) determine charge from anion charge Alternatively, use common name 3. Nonmetal anion Nonmetal name ended with ide: Chloride, Oxide Example: Iron(II) chloride, Copper(I) oxide 20

21 How to find the charge on metal ions with variable charge? Example: Name Compound Fe 2 O 3 Since 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 +3 Name: iron(iii) oxide Key: knowing the charge on ANIONs! 21

22 Example: Naming variable charge metal compound Fe 2 O 3 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 22

23 Practice: Naming Ionic compounds HgF 2 CuI 2 Cr 2 S 3 SnCl 4 Mg 3 N 2 Hg 2 Cl 2 23

24 Naming Ionic compounds Hints: find type II ion charge from anion HgF 2 : Two F = 2 Hg = +2 CuI 2 : Two I = 2Cu = +2 CaCl 2 : both fixed charges Cr 2 O 3 : Three O 2 = 6 Cr = +3 SnBr 4 : Four Br = 4 Sn = +4 Mg 3 N 2 : both fixed charges Ag 2 S : both fixed charges 24

25 Answer key: names of ionic compounds HgF 2 = Mercury(II) fluoride CuI 2 = copper(ii) iodide CaCl 2 = calcium chloride Cr 2 O 3 = chromium(iii) oxide SnBr 4 = tin(iv) bromide Mg 3 N 2 = magnesium nitride Ag 2 S = silver sulfide 25

26 Polyatomic Ions symbol of the polyatomic ion called nitrate symbol of the polyatomic ion called sulfate Mg(NO 3 ) 2 CaSO 4 compound called magnesium nitrate implied 1 subscript on magnesium compound called calcium sulfate implied 1 subscript on calcium parentheses to group two NO 3 s no parentheses for one SO 4 26

27 Polyatomic Ions: Nitrate NO 3, Sulfate SO 4 2 subscript indicating two NO 3 groups no subscript indicating one SO 4 group Mg(NO 3 ) 2 CaSO 4 compound called magnesium nitrate compound called calcium sulfate implied 1 subscript on nitrogen, total 2 N stated 3 subscript on oxygen, total 6 O implied 1 subscript on sulfur, total 1 S stated 4 subscript on oxygen, total 4 O 27

28 Polyatomic Anions: ATE ions CO 3 2 NO 3 carbonate nitrate SiO 3 2 PO 4 3 SO 4 2 ClO 3 silicate phosphate sulfate chlorate AsO 4 3 SeO 4 2 BrO 3 arsenate selenate bromate IO 3 iodate 28

29 Periodic Pattern of Polyatomic Ions ate groups IIIA IVA VA VIA VIIA 3 2 BO 3 CO 3 NO SiO 3 PO 4 SO 4 ClO 3 AsO 4 3 SeO 4 2 TeO 4 2 BrO 3 IO 3 29

30 Patterns for Polyatomic Ions 1. elements in the same Group form similar polyatomic ions same number of O s and same charge ClO 3 = chlorate (1 charge) BrO 3 = bromate (1 charge) 2. if the polyatomic ion starts with H, the name adds hydrogen prefix before name and add 1 to the charge CO 3 2 = carbonate HCO 3 1 = hydrogen carbonate 30

31 Patterns for Polyatomic Ions ate ion chlorate = ClO 3 ate ion + 1 O same charge, per prefix perchlorate = ClO 4 ate ion 1 O same charge, ite suffix chlorite = ClO 2 ate ion 2 O same charge, hypo prefix, ite suffix hypochlorite = ClO 31

32 Polyatomic Anions: ite, hypo ite, (ate), per ate ClO hypochlorite NO 2 PO 3 3 SO 3 2 ClO 2 nitrite phosphite sulfite chlorite NO 3 PO 4 3 SO 4 2 ClO 3 nitrate phosphate sulfate chlorate ClO 4 perchlorate 32

33 ATE/ITE ions in Our Lives ClO (bleach) NO 2 PO 3 3 SO 3 2 ClO 2 (preserve meat) (plant medicine) (wine, oxygen buster) (bleach, disinfect) NO 3 PO 4 3 SO 4 2 ClO 3 (fertilizer, explosives) (bone/teeth, fertilizer, soda) (plaster, car battery, sea salt) (older pyrotechnics) ClO 4 (pyrotechnics, solid fuel rocket) 33

34 Polyatomic Ions to Remember Name Formula acetate C 2 H 3 O 2 carbonate CO 3 2 hydrogen carbonate (aka Bicarbonate) HCO 3 hydroxide OH nitrate NO 3 nitrite NO 2 permanganate MnO 4 chromate CrO 4 2 dichromate Cr 2 O 7 2 ammonium NH 4 + Name Formula hypochlorite ClO chlorite ClO 2 chlorate ClO 3 perchlorate ClO 4 sulfate SO 4 2 Hydrogen sulfate (aka Bisulfate) HSO 4 sulfite SO 3 2 Hydrogen sulfite (aka Bisulfite) HSO 3 cyanide CN 34

35 Polyatomic Ions in Our Lives C 2 H 3 O 2 CO 3 2 HCO 3 OH MnO 4 CrO 4 2 CN NH 4 + In vinegar as acetic acid Soda drink Baking soda, baking power, acid spill neutralizer In liquid plumber/drano as NaOH Disinfectant, aging for movie making Chrome plating (faucet, etc.) Highly Poisonous; Plant seeds; blue pigment Fertilizer; metabolic waste from animals 35

36 Other Polyatomic Ions in Our Lives ClO (bleach) NO 2 PO 3 3 SO 3 2 ClO 2 (preserve meat) (plant medicine) (wine, oxygen buster) (bleach, disinfect) NO 3 PO 4 3 SO 4 2 ClO 3 (fertilizer, explosives) (bone/teeth, fertilizer, soda) (plaster, car battery, sea salt) (older pyrotechnics) ClO 4 (pyrotechnics, solid fuel rocket) 36

37 Compounds Containing Polyatomic Ions Fixed charge metal cation + Polyatomic ion: NaNO 3 Variable charge metal cation + Polyatomic ion: CuSO 4 Polyatomic cation + Nonmetal ion (ide): NH 4 Cl Polyatomic cation + Polyatomic ion: (NH 4 ) 2 SO 4 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 37

38 Example Naming Ionic with Polyatomic Ion Na 2 SO 4 1. Ionic or covalent compound? 2. Ionic: fixed charge or variable charge metal cation? 3. fixed charge metal cation: Name accordingly. Sodium sulfate 38

39 Example Naming Ionic with Polyatomic Ion Fe(NO 3 ) 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 anion Note: what is the name and charge on NO 3? 4. Name accordingly. Iron(III) nitrate 39

40 Practice: Naming Ionic compounds Hg 2 SO 4 CuClO 3 Zn(NO 3 ) 2 FeCO 3 Sn(SO 3 ) 2 CoPO 4 Al(ClO 4 ) 3 40

41 Hints: Naming Ionic compounds Hg 2 SO 4 : charge of sulfate = 1 CuClO 3 : charge of chlorate = 1 Zn(NO 3 ) 2 charge of nitrate = 1 FeCO 3 : charge of carbonate = 2 Sn(SO 3 ) 2 : charge of sulfite = 1 CoPO 4 : charge of phosphate = 3 Al(ClO 4 ) 3 : charge of perchlorate = 1 41

42 Keys: Naming Ionic compounds Hg 2 SO 4 : mercury(i) sulfate CuClO 3 : copper(i) chlorate Zn(NO 3 ) 2 zinc nitrate FeCO 3 : iron(ii) carbonate Sn(SO 3 ) 2 : tin(iv) sulfite CoPO 4 : cobalt(iii) phophate Al(ClO 4 ) 3 : aluminum perchlorate 42

43 Review: Naming Compounds CuSO 3 AgClO Al 2 S 3 FeI 2 Sn(NO 3 ) 4 Ba 3 (PO 4 ) 2 (NH 4 ) 2 S copper(ii) sulfite silver hypochlorite aluminum sulfide iron(ii) iodide tin(iv) nitrate barium phosphate ammonium sulfide 43

44 Write Chemical Formula using the charge of known ions Example: Compound between Ca 2+ and PO 4 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 Ca 3 (PO 4 ) 2 44

45 Write Chemical Formula using the charge of known ions CrissCrossSimplify : The charge of an ion turns into the subscript (the number) of the counterpart ion Pb 4+ O 2 Pb 2 O 4 Since the subscripts in an ionic compound represents the RATIO among the ions, the subscripts need to be simplified when there is common denominator Pb 2 O 4 PbO 2 45

46 Key for Writing formulas (I): use crisscrossreduce copper(ii) chloride CuCl 2 aluminum oxide Al 2 O 3 magnesium phosphide Mg 3 P 2 iron(ii) bromide FeBr 2 lead(ii) sulfide FeS zinc iodide ZnI 2 sodium nitride Na 3 N 46

47 Practice: Write Chemical Formulae Chromium(II) Chloride Cesium phosphate Lead(II) oxide Zinc nitrate Iron(III) sulfite Strontium nitride Ammonium carbonate 47

48 Key: Write Chemical Formulae Chromium(II) Chloride Cesium phosphate Lead(II) oxide Zinc nitrate Iron(III) sulfite Strontium nitride Ammonium carbonate CrCl 2 Cs 3 PO 4 PbO Zn(NO 3 ) 2 Fe 3 (SO 3 ) 2 Sr 3 N 2 (NH 4 ) 2 CO 3 48

49 Key: Writing formulas (I) copper(i) sulfate: Cu 2 SO 4 aluminum chlorate: Al(ClO 3 ) 3 magnesium phosphate: Mg 3 (PO 4 ) 2 iron(ii) carbonate : FeCO 3 lead(ii) acetate: Pb(C 2 H 3 O 2 ) 2 zinc sulfite : ZnSO 3 sodium nitrite: NaNO 2 Nitrogen gas: N 2 49

50 More on Writing formulae copper(ii) sulfate aluminum perchlorate hydroiodic acid iron(iii) bromide Diphosphorus pentoxide lead(iv) nitride zinc carbonate helium gas 50

51 Key: Writing formulae copper(ii) sulfate CuSO 4 aluminum perchlorate Al(ClO 4 ) 3 hydroiodic acid HI iron(iii) bromide FeBr 3 Diphosphorus pentoxide P 2 O 5 lead(iv) nitride Pb 3 N 4 zinc carbonate ZnCO 3 ammonium nitrite NH 4 NO 2 helium gas He 51