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
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
• Law of Definite Proportions
– Atoms usually combine in small integer multiples
– Inorganic common ratios are 1 to 5
• NaCl, CaCl2, Al2O3 , H2SO4, PCl5
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
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-
NaCl dissolving in water
Each ion “solvated” by water molecules, attracted to
oppositely charged ends of water molecules
Equal numbers of Na+ & Cl- ions in solution
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
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
Non-Metal Compounds
• Many combinations involve Oxygen
– CO2, NO2, SO2, etc.
• Naming conventions
– Non-oxygen element named first
• If multiple atoms, use multiplier wording
• Di, tri, tetra, penta, … (mono usually not used)
– Oxygen next, with multiplier wording
• Mono, di, tri, tetra, ….
– A few examples
• Carbon dioxide = CO2
• Carbon Monoxide = CO
• Dinitrogen pentoxide = N2O5
Nomenclature of multiple additions
• Mono (one to add, “monogamous”, “monopole”)
– Carbon Monoxide, is CO (C≡O)
• Di (two to add, think “dipole”, “diode”)
– Carbon Dioxide, is CO2 (O=C=O)
• Tri (three to add, “trimester”, “triangle”, “tritium”)
– Nitrogen Tri-Iodide, is NI3
• Tetra (4 to add, think “tetrahedron”)
– Carbon Tetrachloride, is CCl4
• Penta (5 to add, think “pentagon”, “pentameter”)
– Phosphorus Pentachloride, is PCl5
• Hexa (6 to add, “hexagon”, “hexagonal”)
– Uranium Hexaflouride, is UF6
Single Element Ions
• Cations, positively (+) charged elements
– From “cathode”, the negative battery pole
– Positive (+) ions attracted to (-) cathode
– Mostly metals which lost ≥1 electrons
• Na+, Ca2+, Fe3+, etc.
• Anions, negatively (-) charged elements
– From “Anode”, the positive battery pole
– Negative (-) ions attracted to (+) Anodes
– Mostly non-metals which gained ≥1 electron
• Cl-, Br-, O2-, etc.
Why the terms “Cation”, “Anion” ?
Cations (+) attracted to Cathode (-)
Anions (-) attracted to Anode (+)
What’s a Cathode …
From the Greek work kathodos … “way down”
Electrode where chemical reduction occurs, gain electrons.
Cathodes emit electrons (diodes, CRT)
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
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
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)
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
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
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
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
Multi-Atom (poly atomic) molecules
• Many Anion combinations involve Oxygen
– Nitrite, NO21– Sulfite, SO32– Carbonate, CO32– Chlorate, ClO31– Phosphate, PO43…. And a lot more !
Nitrate, NO31Sulfate, SO42BiCarbonate, HCO31-
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
Polyatomic ions, +1 charge
Tetrahedral ammonium: N has 5 electrons, H has 1, total = 9
Total deployed is 8, so one “went missing”, charge is +1
Hydronium 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
Hydronium Ion
Polyatomic Anions, -1 charge
For NO31-, N has 5 electrons, O has 6, total is 18+5=23
Total deployed = 24, so 1 extra electron = -1 charge
For NO2-1, N has 5 electrons, O has 6, total is 12+5=17
Total deployed = 18, so 1 extra electron = -1 charge
Polyatomic Anions, -2 charge
For SO42-, S has 6 electrons, O has 6, total is 5*6=30
Total deployed = 32, so 2 extra electron = -2 charge
For SO32-, S has 6 electrons, O has 6, total is 4*6 =24
Total deployed = 26, so 2 extra electrons = -2 charge
Preferred valence often the maximum
• Nitrite would rather be Nitrate
– NO2- adds 1 oxygen, N 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- adds 1 oxygen, S 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)
Polyatomic Anions, Carbonate
For CO32-, C has 4 electrons, O has 6, total is 4+18=22
Total deployed = 24, so 2 extra electron = -2 charge
For HCO31-, C=4, 3O=18, H=1 so total =23
Total deployed = 24, so 1 extra electron = -1 charge
Polyatomic Anions, Phosphate
For PO43-, P has 5 electrons, O has 6, total is 5+24=29
Total deployed = 32, so 3 extra electron = -3 charge
For HPO42-, P=5 electrons, O=6, H=1, total is 5+24+1 =30
Total deployed = 32, so 2 extra electrons = -2 charge
Formula Writing
• Polyatomic ions behave like other anions
– Cl-1, NO3-1, SO4-2
• Use parenthesis around the polyatomic ion
– Avoids confusion what multiple is involved
– Ca(NO3)2 … not CaNO32
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
Sn++, Sn(II), or Stannous
Mn++, Mn(II), or Managnous
Cr++, Cr(II), or Chromous
versus Fe+++, Fe(III), or Ferric
versus Sn++++, Sn(IV) or Stannic
vs Mn++++, Mn(IV), or Manganic
versus Cr+++, Cr(III), or Chromic
• Latin Names not precise
– No valence numbers, only words
– Numeric values inconsistent
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
Valence is
Valence is
Valence is
+1 in HClO
+3 in HClO2
+5 in HClO3
+7 in HClO4
Hypochlorous acid
Chlorous acid
Chloric acid
Perchloric acid
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
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`
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
Los Alamos National Laboratory's Periodic Table
Group**
Period
1
IA
1A
2
3
1.008
3
4
H
Li
Be
6.941
9.012
11
12
Na Mg
22.99
4
5
8
9
10
3
4
5
6
7
11 12
------- VIII IIIB IVB VB VIB VIIB
IB IIB
-----3B
4B 5B 6B
7B
1B 2B
------- 8 ------
20
21
Ca
Sc
39.10
40.08
37
38
Rb
Sr
85.47
87.62
Cs
87
Fr
(223)
56
88
6
7
8
9
B
C
N
O
F
22
23
24
25
26
27
28
29
30
13
14
Al Si
32
Y
40
41
42
44
45
46
47
48
49
50
72
73
74
(98)
75
17
18
Cl
Ar
33
34
35
51
52
53
I
101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9
76
77
78
79
80
81
82
83
84
85
Pt Au Hg Tl Pb Bi Po At
138.9 178.5 180.9 183.9 186.2 190.2 190.2 195.1 197.0 200.5 204.4 207.2 209.0 (210) (210)
107
108
109
86
Rn
(222)
116
118
---
()
()
()
59
60
61
62
63
64
111
Xe
131.3
---
(257) (260) (263) (262) (265) (266)
110
54
114
58
106
83.80
---
Lanthanide
Series*
105
36
Kr
112
(227)
104
39.95
Ra Ac~ Rf Db Sg Bh Hs Mt --- --- --(226)
89
Ne
20.18
S
Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te
88.91 91.22 92.91 95.94
57
43
10
16
44.96 47.88 50.94 52.00 54.94 55.85 58.47 58.69 63.55 65.39 69.72 72.59 74.92 78.96 79.90
39
4.003
15
26.98 28.09 30.97 32.07 35.45
31
2
He
P
Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br
Ba La* Hf Ta W Re Os Ir
137.3
5
10.81 12.01 14.01 16.00 19.00
19
132.9
7
24.31
13
14
15 16
17
IIIA IVA VA VIA VIIA
3A 4A 5A 6A 7A
K
55
6
8A
2
IIA
2A
1
1
18
VIIIA
()
()
()
65
66
67
68
69
70
71
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
140.1 140.9 144.2 (147) 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.0 175.0
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 !
Stopping point for 32A
• Now to the nomenclature dry lab
• We’ll use OLD manual, $6.50 at bookstore
– Inexpensive because we print it in-house
• Page 58-69 in Fall 2009 edition
– Pages 58-62 is background material
– Pages 63-69 are the turn-in sheets
– Work with partners, get a good start on each page so
you know how to finish after lab.
– Use Google, Wikipedia, other great web resources
– Don’t copy from others, often a wrong answer source
– Due next week