Ionic Compounds: Bonding Nomenclature Edward Wen 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 Lewis Bonding Theory Atoms bond with each other because bonding results
in a more stable Electron Configuration, aka Nobel Gas Configuration (1s2) or (ns2np6) How to achieve NG configuration? 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 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 Na Mg Al Si N P O S
F Cl Ne Ar 4 Everyone Atom Want to Be Like a Noble Gas! Alkali Metals (Group IA, valence electron ns1) as a group are the most reactive metals they react with many things and do so rapidly Halogens (Group VIIA, 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 (noble gas configuration) 5 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 Na Atoms Electron Config [Ne]3s1
Ion Na+ Ions Electron Config [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] 6 Ionic Bonds Bonding : Metal + Nonmetal Metal loses electrons to form cation (+ charge) Nonmetal gains electrons to form anion (- charge) Ionic bond results from + & - attraction (Coulombic force) larger charge = stronger attraction smaller ion = stronger attraction Lewis Theory allows us to predict the correct formulas of ionic compounds 7 Lewis Symbols of Ions
Cations (Cn+) have no valence electrons Valence electron(s) are Lost in the cation formation Li Li+ + 1e- Anions (An-): 8 valence electrons Electrons gained in the formation of the anion :F: + 1e [:F:] 8 Chemical Formula
Chemical formula: describe the compound by describing the number and type of each atom in the simplest unit of the compound Element represented by its letter symbol #Atoms of each element: the right of the element as a subscript. Two Hydrogen atoms in one H2O molecule. Polyatomic groups (multiple atoms in group, example: CO3) are placed in parentheses if more than one Interactive practice: http://www.thegeoexchange.org/chemistry/naming/index.php http://www.chemistrywithmsdana.org/wp-content/uploads/2012/07/ionic.html 9 Ionic Compounds Ions: 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+ Cl10 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+-O-H+) so it can attract both cation and anion. 11 Ionic Compounds Name: first Cation, followed by Anion example: NaCl Sodium Chloride Cation: Fixed charge vs. Variable charge
Polyatomic ion: ammonium NH4+ Anion: Nonmetal: Chloride Cl-, Oxide O2Polyatomic ion: SO42- , OH- , NO3- 12 Metal Cations with Fixed Charge _______________________ only have one possible charge Charge by position on the Periodic Table IA = +1, IIA = +2, Ag+ (IB), Zn2+(IIB) Al3+(IIIA) Name is the same as the element Ag+ : silver ion Ca2+: calcium ion 13
Metal Cations with Variable Charges Common Examples: Fe2+/3+, Cu+/2+, Cr3+/6+, Mn2+/4+, Mn2+/4+, Pb2+/4+, Sn2+/4+, etc ) Name with Roman numeral to indicate charge Cu+: _____________ Pb4+: _____________ Or use common name (lower charge ous, higher charge ic) Cu+: cuprous Cu2+: cupric Fe2+: ferrous Fe3+: ferric 14 Metal Cations: Remember the fixed charge cations! = Fixed charge = Variable charge
Al Zn Ag Monatomic Nonmetal Anion (A ) n- How much is the charge? the position on the Periodic Table Name of the anion: ending with ide 5A = -3 6A = -2 7A = -1 Nitride = O2- = Fluoride =
P3- = Sulfide = Cl- = 16 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 = 17 Name of Ionic Compounds Cation: Fixed charge cation: Na+ => Sodium Variable charge cation = metal name(charge):
Fe3+ => Iron(III) Or use Common Name: Fe3+ => Ferric Polyatomic ion : NH4+ => Ammonium Anion: Nonmetal anion: -ide, O2- => oxide Polyatomic ion: SO42- => Sulfate 18 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. 19 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 How to find the charge on metal ions with variable charge? Example: Find the charge of metal in Fe2O3 Since the sum of all charges equals zero, the charge on iron ions are unknown and oxide ion has 2 charge, then we have Key: knowing the charge on ANIONs! 21
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. ________________ 22 Group Practice: Naming Ionic compounds HgF2 CuI2 Cr2S3 SnCl4 Mg3N2 Hg2Cl2
symbol of the polyatomic ion called nitrate symbol of the polyatomic ion called sulfate Mg(NO3)2 CaSO4 compound called magnesium nitrate compound called calcium sulfate implied 1 subscript on magnesium parentheses to group two NO3s implied 1 subscript
on calcium no parentheses for one SO4 25 Polyatomic Ions: Nitrate NO3-, Sulfate SO42subscript indicating two NO3 groups no subscript indicating one SO4 group Mg(NO3)2 CaSO4 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 26 Periodic Pattern of Polyatomic Ions -ate groups IIIA 3BO3 IVA VA
2CO3 NO3 2SiO3 3- PO4 3AsO4 VIA VIIA 2SO4 ClO3
2SeO4 BrO3 2TeO4 - IO3 27 Patterns for Polyatomic Ions 1. elements in the same Group form similar polyatomic ions same number of Os 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 28 Patterns for Polyatomic Ions -ate ion chlorate = ClO3- -ate ion + 1 O same charge, per- prefix perchlorate = ClO4- -ate ion 1 O same charge, -ite suffix chlorite = ClO2- -ate ion 2 O same charge, hypo- prefix, -ite suffix hypochlorite = ClO29 Polyatomic Anions: -ite, hypo- -ite, (-ate), per- -ate ClOhypochlorite
2 32 Other Polyatomic Ions in Our Lives C 2 H 3O 2 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 33
Other Polyatomic Ions in Our Lives ClO(bleach) NO2- PO33- SO32- ClO2- (preserve meat) (plant medicine) (wine, oxygen buster) (bleach, disinfect)
fuel rocket) 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 35 Example Naming Ionic with Polyatomic Ion Na SO 2 Ionic or covalent compound? 4 1.
2. Ionic: fixed charge or variable charge metal cation? 3. fixed charge metal cation: Name accordingly. 36 Example Naming Ionic with Polyatomic Ion Fe(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 anion Note: what is the name and charge on NO3? 4. Name accordingly. 37 Practice: Naming Ionic compounds Hg2SO4 CuClO3
Zn(NO3)2 FeCO3 Sn(SO3)2 CoPO4 38 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 ion Pb4+ O2 ________ 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 ________ 39
Write Chemical Formula using the charge of known ions Example: Compound between Ca2+ and PO43- 40 Practice: Write Chemical Formulae Cesium phosphate Lead(II) oxide Zinc nitrate Iron(III) sulfite Strontium nitride
Ammonium carbonate 41 Naming Ionic compounds Hints: find type II ion charge from anion HgF2 : CuI2 : Two F- = -2 Hg = +2 Two I- = -2 Cu = +2 CaCl2 : both fixed charges Cr2O3 : Three O2- = -6 Cr = +3 SnBr4 : Four Br- = -4
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