Mixtures

1. Mixtures • Mixtures are physical (NOT chemical) combinations • Many mixtures have NO chemical reaction potential • Sugar or Salt dissolved in water • Solder, a mixture of Tin and Lead • Unlimited number of potential combinations • Some mixtures have chemical reaction potential • Rocket Propellants (e.g. zinc + sulfur) • Mixture of oxidizer and combustible material • Gunpowder (Charcoal + Sulfur + Potassium Nitrate) • Stable for hundreds of years until ignited • Thermite (iron oxide + aluminum powder) • Reacts yielding liquid iron to weld railroad track • Hydrogen and Oxygen, gasoline and air • Requires an initiator (e.g. heat from spark or flame) • Other mixtures are inherently unstable • Metallic Sodium and water react violently • Liquid rocket propellants burn when mixed • Acids and Bases neutralize each other

2. Thermite Reaction Al + Fe2O3  Al 2O3 + FeAn “unstable” mixture reacts to create new compounds

3. Compounds • Inorganic compounds, “entangled elements” • Chemical reaction creates bonding + heat energy • Constituents are no longer mechanically separable • Creation of a new material unlike the constituents • Gaseous hydrogen and oxygen burn to form liquid water • Metallic sodium and chlorine gas combine to form table salt • Aluminum and “rust” create liquid iron + lots of heat • Law of Definite Proportions • Atoms usually combine in small integer multiples • Inorganic common ratios are 1 to 5 • NaCl, CaCl2, Al2O3, H2SO4, PCl5

4. Molecules, Ions, Chemical Bonds • Ionic Bonds • Complete charge separation • Electrons relocated from donor to acceptor atoms • Unlike atoms involved (e.g. Sodium Chloride) • Opposite sides of periodic table • Dissolve in water to form charged ions • Ionic crystals formed when no solvent • Electrostatic “binding energy” holds crystal together • No distinct partnering • All Na and Cl ions are equivalent in solution or solid crystal • Neutral charge balance, but joined pairs of ions

5. Los Alamos National Laboratory's Periodic Table

6. Opposite charge attraction A 3-D array of ions Ionic CrystalsHeld together by electrostatic attraction

7. Molecules, Ions, Chemical Bonds • Ionic Bonds • “Cation” is positively charged ion • Attracted to “Cathode” which is negative pole • Typically a metal with 1-3 missing electrons • Na1+, Ca2+, Fe3+ • “Anion” is negatively charged ion • Attracted to “Anode” which is a positive pole • Typically a halogen or oxide with 1-2 extra electrons • F1-, Br1-, O2- … • Polyatomic Anions also very common • These are very stable molecular species • NO31-, SO42-, PO43-

8. NaCl dissolving in waterEach ion “solvated” by water molecules, attracted to oppositely charged ends of water moleculesEqual numbers of Na+ & Cl- ions in solution

9. Molecules, Ions, Chemical Bonds • Covalent Bond • Shared electrons between atoms • Pair of electrons involved, one from each atom • Same kind of atoms often linked to each other • Carbon-carbon electron sharing very common • Diatomic elements: O2, H2, N2, F2 … not He, Ne, Xe • “Octet Rule” describes stable configurations • Total of 8 electrons around atom most stable • Exception is Hydrogen = 2 for complete “s” shell • Can achieve an octet via sharing • My one + your one = two to share • Carbon is ideal candidate for sharing • 4 electrons to share with 4 other elements

10. Oxygen forms O2 Atoms 68 electrons Methane, CH4 Carbon shares 8, hydrogen 2 Covalent bondingInvolves SHARED electrons

11. Los Alamos National Laboratory's Periodic Table

12. Molecules, Ions, Chemical Bonds • Why not diatomic He, Ne, Ar, Kr … ? • These already have a full octet • No need to share for 8 outer shell electrons • Full outer shell means INERT • No chemical reactions if no electrons to transfer • NO compounds form with He, Ne, etc. • Can ionize (remove electrons) with high voltage • Electrons fall back with emission of light • Low pressure Neon (pink) used in signs • Argon (blue) used in high power lasers • Xenon (white) for camera’s electronic flash

13. Why is the electron negative ? • Benjamin Franklin responsible ! • Published kite in a storm experiment in 1780 • Nobody really knew what electricity was • A dangerous experiment, people killed repeating it • He applied terms “positive” and “negative” • “Electrical Fluid” was term used at the time • (+) and (-) Used for batteries, electrolysis • Unfortunately “positive” is backwards • Assumption of flow (+) to (-) was wrong • … but we kept the polarity definitions • Electrons go the other way, are therefore (-) • See wikipedia on Benjamin Franklin

16. Element Ionic charges • Alkali metals (1st column) have single (+) charge • Na+, K+ , Li+ • Usually do NOT write the number for single charge • Alkalai Earth metals (2nd col.) have charge (+2) • Ca 2+ , Mg 2+ • Transition metals often have multiple valences • Iron can lose 2 or 3 electrons, Fe2+ or Fe3+ • Similar situation with Mn, Cr, Sn, etc. • Old Latin names indicated degree of valence • “-ic” at end was/is highest valence state (mostly) • But not always the same valence numerical value • Ferric is +3, Stannic is +4 • “-ous” at end was/is lowest valence state (mostly) • Not always the same numerical value

17. Los Alamos National Laboratory's Periodic Table

18. Formation of Compounds • Binary Compounds • Cation + Anion  neutral molecule • Simple ratios = “law of multiple proportions” • Atom quantities must yield charge balance • 2 * Fe3+ + 3 * O2- Fe2O3 • H2SO4 2H++SO42- • Molecules must be “real” materials • Use multiplier to clear fractions (e.g. ½ O2)

19. Naming Compounds • Binary Inorganic compounds • Compound name starts with an element name • Same names & symbols on periodic chart • Sodium (Na), Iron (Fe), Cadmium (Cd) • Cation element (+), then Anion (-) name • Chlorine, oxygen, sulfur • Anion (-) in binary compound ends in –ide • Sodium Chloride • Iron Oxide, • Cadmium Sulfide

20. Binary Halogen Acids • For halogen acids, “hydro” is prefix used • Hydrochloric Acid = HCl • Avoids confusion with Chloric Acid = HClO3 • Binary Halogen Acids include • Hydrofluoric Acid = Hydrogen Fluoride = HF • Hydrochloric Acid = Hydrogen Chloride = HCl • Hydrobromic Acid = Hydrogen Bromide = HBr • Hydroiodic Acid = Hydrogen Iodide = HI

21. Formula Writing • Cation first (usually a metal or hydrogen) • Hydrogen, H (valence +1) • Calcium, Ca (valence +2) • Aluminum, Al (valence +3) • Anion follows (often a halogen, or gas) • Sulfur  Sulfide (valence -2) • Chlorine  Chloride (valence -1) • Oxygen  Oxide (valence -2) • Add the two element names, formula is in atomic ratios • Hydrogen Sulfide, H2S ratio follows valence, 2:1 • Calcium Chloride, CaCl2 ratio follows valence, 1:2 • Aluminum Oxide, Al2O3 ratio follows valence, 2:3

22. Formula Writing • Atomic ratios are simple numbers (1, 2, 3 …5) • Find a common denominator number for electrons • Multiply cation valence times anion valence • Aluminum (+3) * Oxygen (-2) = 6 total electrons involved • Divide each valence into the common denominator • 6/3 for aluminum = 2, • 6/2 for oxygen =3 • These values are the ratios of the elements • Al2O3

23. Multi-Atom (poly atomic) molecules • Many Anion combinations involve Oxygen • Nitrite, NO21- Nitrate, NO31- • Sulfite, SO32- Sulfate, SO42- • Carbonate, CO32- BiCarbonate, HCO31- • Chlorate, ClO31- • Phosphate, PO43- …. And a lot more !

24. Formation of ions NH3 + HCl  NH4+ + Cl-

25. Polyatomic Oxygen Anions • Oxygen forms group around other elements • 2, 3, 4 oxygen clusters surrounding another atom • Stable configuration due to electron sharing • Sharing fills outer electron (valence) shell • “Octet Rule”, 8 is “magic number” for full shells • Shells of 8 creates exceptionally stable configuration • Anion Groups exist with extra electrons • Gather as many as needed for full shells • “owning” or “sharing” electrons is equivalent • Sharing is as good as ownership ! • Excess electrons give ion a negative charge

26. Polyatomic ions, +1 chargeTetrahedral ammonium: N has 5 electrons, H has 1, total = 9Total deployed is 8, so one “went missing”, charge is +1Hydronium is proton (+1) attached to water, O=6 elect, H=1, total =9 Total deployed is 8, so one “went missing”, ionic charge is +1

27. Hydronium Ion

28. Polyatomic Anions, -1 chargeFor NO31-, N has 5 electrons, O has 6, total is 18+5=23Total deployed = 24, so 1 extra electron = -1 chargeFor NO2-1, N has 5 electrons, O has 6, total is 12+5=17Total deployed = 18, so 1 extra electron = -1 charge

29. Nitrate Formation from elements1 additional electron needed to fill all shells of 8,meeting octet rule requires (-1) charge on anion

30. Alternative Nitrate Representations“Ball & Stick” easy to model and understand “Bubbles” represent electron clouds, sizeWe willuse computer simulations in an experiment

31. Polyatomic Anions, -2 chargeFor SO42-, S has 6 electrons, O has 6, total is 5*6=30Total deployed = 32, so 2 extra electron = -2 chargeFor SO32-, S has 6 electrons, O has 6, total is 4*6 =24Total deployed = 26, so 2 extra electrons = -2 charge

32. Sulfate Formation from elements2 additional electrons needed to fill all shells of 8,meeting octet rule requires (-2) charge on anion

33. Preferred valence often the maximum • Nitrite would rather be Nitrate • NO2- adds 1 oxygen, becomes NO3- • Nitrogen valence goes (+3)  (+5) • All valence electrons consumed at (+5) • Makes it useful as a preservative in sausage • Nitrite consumes oxygen before the meat does • Sulfite would rather be Sulfate • SO3 2- adds 1 oxygen, becomes SO42- • Sulfur valence goes (+4)  (+6) • All valence electrons consumed at (+6) • Also a preservative, used in wine • Sulfite consumes oxygen before the wine does • Prevents wine into vinegar (until sulfite runs out)

34. Polyatomic Anions, CarbonateFor CO32-, C has 4 electrons, O has 6, total is 4+18=22Total deployed = 24, so 2 extra electron = -2 chargeFor HCO31-, C=4, 3O=18, H=1 so total =23Total deployed = 24, so 1 extra electron = -1 charge

35. Polyatomic Anions, PhosphateFor PO43-, P has 5 electrons, O has 6, total is 5+24=29Total deployed = 32, so 3 extra electron = -3 chargeFor HPO42-, P=5 electrons, O=6, H=1, total is 5+24+1 =30Total deployed = 32, so 2 extra electrons = -2 charge

36. Formula Writing • Polyatomic ions behave like other anions • Cl-1, NO3-1, SO4-2 • Use parenthesis around the polyatomic ion • Subscript beneath parenthesis • Tells how may polyatomic ions involved • Avoids confusion what multiple intended • For Calcium Nitrate: • Ca(NO3)2 is correct • … not CaNO32 • … not Ca2NO3

37. Multiple Valence Cations • Some elements have multiple valences • Lose up to all electrons in outer shell • Old Latin names indicate valence • Fe++, Fe(II), or Ferrous versus Fe+++, Fe(III), or Ferric • Sn++, Sn(II), or Stannous versus Sn++++, Sn(IV) or Stannic • Mn++, Mn(II), or Managnous vs Mn++++, Mn(IV), or Manganic • Cr++, Cr(II), or Chromous versus Cr+++, Cr(III), or Chromic • Latin Names not precise • No valence numbers, only words • Numeric values inconsistent

38. Electronic Configurationssome elements can either lose or gain electrons

39. Oxides of Chlorine • Chlorine an unusual case, (+) or (-) valence • As halogen it exhibits (-1) charge • Due to gaining one electron to fill octet • Valence is -1 in HCl, Hydrochloric Acid • NaCl, CaCl2, AlCl3, etc. • Another possibility is to lose electrons • Relatively unstable and reactive compounds • 7electrons in outer shell, 5 more loosely held • Valence is +1 in HClO Hypochlorous acid • Valence is +3 in HClO2 Chlorous acid • Valence is +5 in HClO3 Chloric acid • Valence is +7 in HClO4 Perchloric acid

42. More on Latin Names • xxx-”ic” acid yields xxx-”ate” anion • Nitric acid HNO3 yields nitrate ion, NO3- • Sulfuric acid H2SO4 yields sulfate ion, SO42- • Chloric acid HClO3 yields Chlorate ion, ClO3- • Originally the highest valence state observed • xxx-”ous” acid yields xxx-”ite” anion • Nitrous acid HNO2 yields nitrite ion, NO2- • Sulfurous acid H2SO3 yields sulfite ion, SO32- • Chlorous acid HClO2 yields chlorite ion, ClO2- • Originally the lowest valence state observed

43. More on Latin Names • What to do after finding MORE valence states than handled by ”ous” and ”ic” suffixes? • Fix is more words to modify existing descriptors • “hypo” and ‘per” adopted to handle the situation • “Hypo”-xxx means 1 less oxygen (below “ous”) • Chlorous acid is HClO2 • Hypochlorous acid is HClO • Sodium Hypochorite (Chlorox) is NaClO • “Per”-xxx means 1 more oxygen (beyond “ic”) • Chloric acid is HClO3 • Perchloric acid is HClO4`

46. What if it’s not in the text? • Look for “family” relationships in columns • Sulfur and Selenium have similar properties they are both in periodic chart column 6A • Sulfate is based on sulfur, SO4- - • Selenium analog is “Selenate” SeO4 - - • Tellurium analog would be “Tellurate TeO4- - • Cesium is similar to Sodium, in column 1A • Sodium Chloride is NaCl, • Rubidium analog would be RbCl • Cesium analog would be CsCl

47. Los Alamos National Laboratory's Periodic Table

48. Valence Naming Summary • Latin Names: Ferrous, Ferric, Chromic, .. • Good = easy to say and type • Bad = inconsistent, no numbers to rely on • Roman Numerals: Fe(III), Sn(IV) • Good = easy to type • Bad = clumsy to say, antiquated Roman Numbering • Plus and Minus signs : Fe++, SO4 - - • Good = intuitive, fast to hand write, clarity • Bad = inconvenient to type, clumsy for large valence values • Arabic character with sign: Fe2+ • Good = intuitive, clarity, good for large valences • Bad = inconvenient to type • Bottom Line … you will run into ALL of these • Be prepared !

49. Nomenclature for 32A • Now to the nomenclature dry lab (no goggles today) • Important issue, learning the language of chemistry • We’ll use the lab manual • Introduction • Tables of ions pages • Naming Matrix, supply BOTH formula +name in box • Naming exercises, page • Binary compounds, page • Use Google, Wikipedia, other great web resources • Collaboration is OK, but don’t just copy from others • You don’t learn much by copying • often a source of wrong answers, • Brain damage, if you learn and remember wrong answers • Due next week