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Introductory ChemistryIntroductory Chemistry, 2, 2ndnd Edition EditionNivaldo TroNivaldo Tro
Chapter 5Molecules andCompounds
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 22
Molecules and CompoundsMolecules and Compounds
CompoundsCompounds = composed of 2 or = composed of 2 or more elements chemically more elements chemically combinedcombined
Properties completely different Properties completely different from component elementsfrom component elements
SaltSalt– Sodium (Na)Sodium (Na) – shiny, reactive, – shiny, reactive,
poisonouspoisonous– Chlorine (Cl)Chlorine (Cl) – pale yellow – pale yellow
gas, reactive, poisonousgas, reactive, poisonous– Sodium chloride (NaCl)Sodium chloride (NaCl) – –
table salt, flavor enhancertable salt, flavor enhancer
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 33
Pure substancesPure substances have have constant compositionconstant composition– all samples of a all samples of a pure pure
substancesubstance contain same contain same elements in same ratios or elements in same ratios or proportions regardless of proportions regardless of sourcesource
– mixturesmixtures have variable have variable compositioncomposition
Law of Constant CompositionLaw of Constant Composition
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 44
Compounds Display Compounds Display Constant CompositionConstant Composition
Water (HWater (H22O)O) decomposed by electrolysis yields decomposed by electrolysis yields
16.0 grams of oxygen to every 2.00 grams of 16.0 grams of oxygen to every 2.00 grams of hydrogen. hydrogen.
Water has a Water has a constantconstant Mass RatioMass Ratio of Oxygen to of Oxygen to Hydrogen of 8.0.Hydrogen of 8.0.
0.8g 2.0
g 0.16
hydrogen of mass
oxygen of mass Ratio Mass
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 55
Formulas Describe CompoundsFormulas Describe Compounds
CompoundCompound = a distinct substance that is = a distinct substance that is composed of atoms of two or more elementscomposed of atoms of two or more elements
FormulasFormulas give the number and type of each give the number and type of each atom in the simplest unit of the compoundatom in the simplest unit of the compound
– Molecules (HMolecules (H22O)O) or or ions (CaClions (CaCl22))
Number of atoms of each element is written to Number of atoms of each element is written to the right of the element as a the right of the element as a subscriptsubscript– if only one atom, 1 subscript is not writtenif only one atom, 1 subscript is not written
Polyatomic groupsPolyatomic groups are placed in parentheses are placed in parentheses
– if more than one, i. e. Caif more than one, i. e. Ca(NO(NO33))22
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 66
Formulas Describe CompoundsFormulas Describe Compounds
Examples:Examples:
water = Hwater = H22O O two atoms of two atoms of
hydrogen and 1 atom of hydrogen and 1 atom of oxygenoxygen
table sugar (sucrose) = Ctable sugar (sucrose) = C1212HH2222OO1111
12 atoms of 12 atoms of CC, 22 atoms of H , 22 atoms of H
and 11 atoms and 11 atoms OO
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 77
Classifying MaterialsClassifying Materials
Atomic elementsAtomic elements = = elements whose particles elements whose particles are single atoms; Na, Ne, are single atoms; Na, Ne, Hg, AgHg, Ag
Molecular elementsMolecular elements = = elements whose particles elements whose particles are multi-atom molecules; are multi-atom molecules; HH22, O, O22, N, N22, Cl, Cl22
88
Molecular ElementsMolecular ElementsCertain elements occur as 2 atom moleculesCertain elements occur as 2 atom moleculesRule of 7’s Rule of 7’s – there are 7 common diatomic elementsthere are 7 common diatomic elements– find the element with atomic number 7, Nfind the element with atomic number 7, N– make a figure 7 by going over to Group 7A, then downmake a figure 7 by going over to Group 7A, then down– don’t forget to include Hdon’t forget to include H22
H2
Cl2
Br2
I2
VIIAVIIAN2 O2 F2
7
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 99
Classifying MaterialsClassifying Materials
Molecular compoundsMolecular compounds = = compounds whose particles compounds whose particles are molecules made of only are molecules made of only nonmetals, i.e. COnonmetals, i.e. CO22
Ionic compoundsIonic compounds = = compounds whose particles compounds whose particles are are cations (+)cations (+) and and anions (-)anions (-), , i.e. NaCli.e. NaCl
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 1010
Molecular CompoundsMolecular Compounds
Two or more Two or more nonmetalsnonmetals, i.e. H, i.e. H22O, O,
COCO22, C, C66HH1212OO66
Smallest unit is a Smallest unit is a moleculemolecule
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 1111
Order of Elements in a FormulaOrder of Elements in a FormulaMetals written firstMetals written first– NaClNaCl
Nonmetals written in order Nonmetals written in order from Table 5.1from Table 5.1– COCO22
– occasional exceptions for occasional exceptions for historical or informational historical or informational reasonsreasons
HH22O, but NaO, but NaOHOH
Order of Listing Order of Listing NonmetalsNonmetalsin Chemical Formulasin Chemical Formulas
Table 5.1Table 5.1
FFOOClClBrBrIISSHHNNPPCC
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 1212
Ionic CompoundsIonic Compounds
MetalsMetals + + nonmetalsnonmetals
No individual No individual molecule units, molecule units, instead have a 3-instead have a 3-dimensional array of dimensional array of cationscations and and anionsanions made of made of formula formula unitsunits
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Molecular View of Elements and CompoundsMolecular View of Elements and Compounds
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 1414
Classify each of the following as either an Classify each of the following as either an atomic element, molecular element, molecular atomic element, molecular element, molecular
compound or ionic compound compound or ionic compound
aluminum, Alaluminum, Al
aluminum chloride, AlClaluminum chloride, AlCl33
chlorine, Clchlorine, Cl22
acetone, Cacetone, C33HH66OO
carbon monoxide, COcarbon monoxide, CO
cobalt, Cocobalt, Co
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 1515
Classify each of the following as either an Classify each of the following as either an atomic element, molecular element, molecular atomic element, molecular element, molecular
compound or ionic compound compound or ionic compound
aluminum, Al aluminum, Al = atomic element= atomic element
aluminum chloride, AlClaluminum chloride, AlCl33 = ionic = ionic
compoundcompound
chlorine, Clchlorine, Cl22 = molecular element= molecular element
acetone, Cacetone, C33HH66O O = molecular compound= molecular compound
carbon monoxide, CO carbon monoxide, CO = molecular = molecular compoundcompound
cobalt, Co cobalt, Co = atomic element= atomic element
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 1616
Major Classes of CompoundsMajor Classes of Compounds
IonicIonic– metal + nonmetalmetal + nonmetal
metal first in formulametal first in formula
Binary IonicBinary Ionic
– compounds with polyatomic ionscompounds with polyatomic ions
MolecularMolecular– 2 nonmetals2 nonmetals
Binary Molecular (or Binary Covalent)Binary Molecular (or Binary Covalent)
– AcidsAcids – formula starts with H – formula starts with Hthough acids are molecular, they behave as ionic though acids are molecular, they behave as ionic when dissolved in waterwhen dissolved in water
may be binary or oxyacidmay be binary or oxyacid
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Binary Ionic Compounds:Binary Ionic Compounds:Writing a correct formulaWriting a correct formula
1. Write down the charges of the 1. Write down the charges of the stable ions with the stable ions with the positive ion positive ion first.first.
Ex: for Chlorine and magnesium
Mg Cl 1-2+
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2. Cross-over charges to get subscripts. 2. Cross-over charges to get subscripts. Drop all +/- signs.Drop all +/- signs.
Ex: for Chlorine and magnesium
Mg Cl1 -2+
1 2
1919
3.3. Reduce/Simplify subscripts to get the Reduce/Simplify subscripts to get the lowest whole number ratio. The subscript lowest whole number ratio. The subscript “1” does not have to be shown.“1” does not have to be shown.
Ex: for Chlorine and magnesium
MgCl2
Ex: calcium and sulfur
Ca+2S-2 Ca2S2cross-over CaSsimplify
2020
How many electrons will an atom lose or gain in an ionic compound?
lose
1 e
-
lose
2 e
-
lose
3 e
-
gain
3 e
-
gain
2 e
-
gain
1 e
-
2121
What will be the charge on the What will be the charge on the “stable ion” formed?“stable ion” formed?
+1+2 +3 -3 -2 -1
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 2222
Rules for Naming Rules for Naming Ionic Ionic CompoundsCompounds from Formula from Formula
Made of Made of cationcation and and anionanionName by simply naming the ionsName by simply naming the ions– If cation is:If cation is:
Type I metal (main group) = metal nameType I metal (main group) = metal nameType II metal (transition element) = metal Type II metal (transition element) = metal name(charge)name(charge)Polyatomic ion = name of polyatomic ionPolyatomic ion = name of polyatomic ion
– If anion is:If anion is:Nonmetal = root of nonmetal name + Nonmetal = root of nonmetal name + ideidePolyatomic ion = name of polyatomic ionPolyatomic ion = name of polyatomic ion
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 2323
Metal CationsMetal Cations
Type IType I – metals whose ions can only metals whose ions can only
have one possible chargehave one possible charge
IA, IIA, (Al, Ga, In)IA, IIA, (Al, Ga, In)– determine charge by position determine charge by position
on the Periodic Tableon the Periodic Table
IA = +1, IIA = +2, (Al, Ga, In IA = +1, IIA = +2, (Al, Ga, In = +3)= +3)
Type IIType II– metals whose ions can have metals whose ions can have
more than one possible more than one possible charge (transition elements)charge (transition elements)
– determine charge by charge determine charge by charge on anionon anion
How do you know a How do you know a metal cation is Type II?metal cation is Type II?
its not Type I !!!its not Type I !!!
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 2424
Determine if the following metals are Type I or Determine if the following metals are Type I or Type II. If Type I, determine the charge on the Type II. If Type I, determine the charge on the
cation it forms.cation it forms.
lithium, Lilithium, Li
copper, Cucopper, Cu
gallium, Gagallium, Ga
tin, Sntin, Sn
strontium, Srstrontium, Sr
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 2525
Determine if the following metals are Type I or Determine if the following metals are Type I or Type II. If Type I, determine the charge on the Type II. If Type I, determine the charge on the
cation it forms.cation it forms.
lithium, Lilithium, Li Type IType I +1+1
copper, Cucopper, Cu Type IIType II
gallium, Gagallium, Ga Type IType I +3+3
tin, Sntin, Sn Type IIType II
strontium, Srstrontium, Sr Type IType I +2+2
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 2626
Determining Charge and Naming Determining Charge and Naming Monatomic Nonmetal AnionsMonatomic Nonmetal Anions
Determine the charge from position on Determine the charge from position on the Periodic Tablethe Periodic Table
To name anion, change ending on the To name anion, change ending on the element name to element name to ––ideide
4A = -44A = -4 5A = -35A = -3 6A = -26A = -2 7A = -17A = -1
C = C = carbidecarbide
N = nitrideN = nitride O = oxideO = oxide F = fluorideF = fluoride
Si = Si = silicidesilicide
P = P = phosphidephosphide
S = sulfideS = sulfide Cl = Cl = chloridechloride
2727
Naming Type I Binary Ionic CompoundsNaming Type I Binary Ionic Compounds
Contain Contain Metal CationMetal Cation + + Nonmetal AnionNonmetal Anion
Metal listed first in formula & nameMetal listed first in formula & name
1.1. name metal cation first, name nonmetal name metal cation first, name nonmetal anion secondanion second
2.2. cation name is the metal namecation name is the metal name
3.3. nonmetal anion named by changing the nonmetal anion named by changing the ending on the nonmetal name to ending on the nonmetal name to -ide-ide
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What is the correct formula and name for What is the correct formula and name for a compound made from:a compound made from:
1. nitrogen and potassium1. nitrogen and potassium
2. magnesium and oxygen2. magnesium and oxygen
3. chlorine and calcium3. chlorine and calcium
4. oxygen and aluminum4. oxygen and aluminum
2929
1. nitrogen and potassiumK3N potassium nitride
2. magnesium and oxygenMgO magnesium oxide
3. chlorine and calciumCaCl2 calcium chloride
4. oxygen and aluminumAl2O3 aluminum oxide
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 3030
Naming Type II Binary Ionic CompoundsNaming Type II Binary Ionic Compounds
Name metal cation first, name nonmetal Name metal cation first, name nonmetal anion secondanion second
Metal cation nameMetal cation name is the metal name is the metal name followed by a followed by a Roman Numeral in Roman Numeral in parentheses to indicate its chargeparentheses to indicate its charge
– determine charge from anion chargedetermine charge from anion charge– Common Type II cations in Table 5.5Common Type II cations in Table 5.5
Nonmetal anion named by changing the Nonmetal anion named by changing the ending on the nonmetal name to ending on the nonmetal name to -ide-ide
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 3131
Example – Naming Binary Ionic, Type II MetalExample – Naming Binary Ionic, Type II Metal
CuClCuCl
1.1. Identify Major ClassIdentify Major ClassCu = metal, on left side of Periodic TableCu = metal, on left side of Periodic Table
Cl = nonmetal, on right side of Periodic TableCl = nonmetal, on right side of Periodic Table
IonicIonic
2.2. Identify the Subclass Identify the Subclass 2 elements, 2 elements,
Binary IonicBinary Ionic
3.3. Is the metal Type I or Type IIIs the metal Type I or Type IICu not in Group IA, IIA, or (Al, Ga, In) Cu not in Group IA, IIA, or (Al, Ga, In) Type II Type II
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 3232
Example – Naming Binary Ionic, Type II MetalExample – Naming Binary Ionic, Type II Metal CuClCuCl
4.4. Identify Identify cationcation and and anionanionClCl = = ClCl-- because it is Group 7 because it is Group 7CuCu = = CuCu++ to balance the charge to balance the charge
5.5. Name the cationName the cationCuCu++ = copper( = copper(II))
6.6. Name the anionName the anionClCl-- = chloride = chloride
7.7. Write the cation name first, then the Write the cation name first, then the anion nameanion name
copper(copper(II) chloride) chloride
3333
Give the formula and name for a Give the formula and name for a compound from Cucompound from Cu+1+1 and sulfur and sulfur
Cu+1 S-2
formula = Cu2S
name = copper(I) sulfide
3434
Give the formula and name for a Give the formula and name for a compound from compound from FeFe+2+2 and and chlorinechlorine
Fe+2 Cl-1 formulaformula = FeClFeCl22
namename = = iron(iron(IIII) chloride) chloride
Give the formula and name for a Give the formula and name for a compound from compound from CuCu+2+2 and and sulfursulfur
Cu+2 S-2 formula = formula = CuSCuS
name = name = copper(copper(IIII) sulfide) sulfide
3535
What is the formula for copper(What is the formula for copper(IIII) ) oxide?oxide?
Cu+2 O-2
formula = CuO
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 3636
Compounds with Compounds with Polyatomic IonsPolyatomic Ions
Polyatomic ionsPolyatomic ions are single ions that are single ions that contain more than one atomcontain more than one atom
Formula: cation first, polyatomic anion or Formula: cation first, polyatomic anion or polyatomic cation, monatomic anionpolyatomic cation, monatomic anion
Name cation first and then anionName cation first and then anion– Non-polyatomic cations named like Type I and Non-polyatomic cations named like Type I and
IIII– Non-polyatomic anions named with Non-polyatomic anions named with ––ideide– Polyatomic ionsPolyatomic ions = use name of polyatomic ion = use name of polyatomic ion
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 3737
Some Common Polyatomic IonsSome Common Polyatomic Ions(be able to recognize these)(be able to recognize these)NameName Formula and ChargeFormula and Chargeacetateacetate CC22HH33OO22
––
carbonatecarbonate COCO3322––
hydrogen carbonatehydrogen carbonate(aka bicarbonate)(aka bicarbonate)
HCOHCO33––
hydroxidehydroxide OHOH––
nitratenitrate NONO33––
nitritenitrite NONO22––
sulfatesulfate SOSO4422––
chloratechlorate ClOClO33––
ammoniumammonium NHNH44++
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 3838
Naming Ionic Compounds with Polyatomic IonNaming Ionic Compounds with Polyatomic Ion NaNa22SOSO44
1.1. Identify Major ClassIdentify Major ClassNa = metal, on the left side of Periodic TableNa = metal, on the left side of Periodic Table
SOSO44 = is a polyatomic ion, = is a polyatomic ion, Ionic Ionic
2.2. Identify the SubclassIdentify the Subclasscompound has 3 elements compound has 3 elements Ionic with Ionic with
Polyatomic IonPolyatomic Ion
3.3. Is the metal Type I or Type IIIs the metal Type I or Type IINa is in Group IA, Na is in Group IA, Type I Type I
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 3939
4.4. Identify the ionsIdentify the ionsNa = NaNa = Na+ + because in Group 1because in Group 1
SOSO44 = SO = SO442-2- a polyatomic ion a polyatomic ion
5.5. Name the cationName the cationNaNa++ = sodium (Type I) = sodium (Type I)
6.6. Name the anionName the anion
SOSO442-2- = sulfate = sulfate
7.7. Write the name of the cation followed by Write the name of the cation followed by the name of the anionthe name of the anion
sodium sulfatesodium sulfate
Naming Ionic Compounds with Polyatomic IonNaming Ionic Compounds with Polyatomic Ion NaNa22SOSO44
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 4040
Naming Ionic Compounds with Polyatomic IonNaming Ionic Compounds with Polyatomic Ion Fe(NOFe(NO33))33
1.1. Identify Major ClassIdentify Major ClassFe = metal, on left side of Periodic TableFe = metal, on left side of Periodic Table
NONO33 = is a polyatomic ion because it is in ( ) = is a polyatomic ion because it is in ( )
IonicIonic
2.2. Identify the SubclassIdentify the SubclassHave 3 elements Have 3 elements Ionic with Polyatomic Ion Ionic with Polyatomic Ion
3.3. Is the metal Type I or Type IIIs the metal Type I or Type IIFe not in Group IA, IIA, or (Al, Ga, In) Fe not in Group IA, IIA, or (Al, Ga, In) Type II Type II
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 4141
Naming Ionic compounds with Polyatomic IonNaming Ionic compounds with Polyatomic Ion
Fe(NOFe(NO33))335.5. Identify the ionsIdentify the ions
NONO33 = NO = NO33-- a polyatomic ion a polyatomic ion
Fe = FeFe = Fe+3+3 to balance the charge of the 3 NO to balance the charge of the 3 NO33-1-1
6.6. Name the cationName the cationFeFe+3+3 = iron( = iron(IIIIII) (Type ) (Type IIII))
7.7. Name the anionName the anion
NONO33-- = nitrate = nitrate
8.8. Write the name of the cation followed by Write the name of the cation followed by the name of the anionthe name of the anion
iron(iron(IIIIII) nitrate) nitrate
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 4242
Rules for Naming Binary Rules for Naming Binary Molecular Compounds Molecular Compounds
Binary molecularBinary molecular compounds = compounds = composed of composed of 2 nonmetal elements2 nonmetal elementsfor binary molecular compound:for binary molecular compound:– name first nonmetalname first nonmetal– then name second nonmetal with then name second nonmetal with ideide
endingending– then give each name a then give each name a prefixprefix to indicate to indicate
number of atoms number of atoms (subscript)(subscript) of each of each element in formulaelement in formula
4343
Naming Binary Molecular Compounds Naming Binary Molecular Compounds
1.1. Name first element in formula first Name first element in formula first – use the full name of the elementuse the full name of the element
2.2. Name the second element in the formula with Name the second element in the formula with an an -ide-ide
– as if it were an anion, as if it were an anion, however, remember these however, remember these compounds do not contain ionscompounds do not contain ions!!
3.3. Use a prefix in front of each name to indicate Use a prefix in front of each name to indicate the number of atomsthe number of atoms
a)a) Never use the prefix Never use the prefix mono-mono- on the first element on the first element
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 4444
Subscript - PrefixesSubscript - Prefixes1 = mono-; 1 = mono-; – not used on first nonmetalnot used on first nonmetal
2 = di-2 = di-3 = tri-3 = tri-4 = tetra-4 = tetra-5 = penta-5 = penta-6 = hexa-6 = hexa-7 = hepta-7 = hepta-8 = octa-8 = octa-drop last “a” if name begins with voweldrop last “a” if name begins with vowel
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 4545
Naming Binary Molecular CompoundsNaming Binary Molecular Compounds BFBF33
1.1. Identify Major ClassIdentify Major ClassB = nonmetal, on right side of Periodic B = nonmetal, on right side of Periodic
TableTable
F = nonmetal, on right side of Periodic F = nonmetal, on right side of Periodic TableTable
MolecularMolecular
2.2. Identify the SubclassIdentify the Subclass2 elements 2 elements Binary Molecular Binary Molecular
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 4646
Naming Binary Molecular CompoundsNaming Binary Molecular Compounds BFBF33
4.4. Name the first element: Name the first element: boronboron5.5. Name the second element with an Name the second element with an –ide–ide
fluorine fluorine fluor fluorideide6.6. Add a prefix to each name to indicate the Add a prefix to each name to indicate the
subscriptsubscriptmonoboron, trifluoridemonoboron, trifluoride
7.7. Write the first element with prefix, then the Write the first element with prefix, then the second element with prefixsecond element with prefix
– Drop prefix Drop prefix monomono from first element from first element
boron trifluorideboron trifluoride
Tro's Introductory Chemistry, Chapter 5Tro's Introductory Chemistry, Chapter 5 4747
Formula MassFormula Mass
Formula massFormula mass = mass of an individual = mass of an individual molecule or formula unitmolecule or formula unit
also known as also known as molecular mass or molecular molecular mass or molecular weightweight
SumSum of the masses of the atoms in a single of the masses of the atoms in a single molecule or formula unitmolecule or formula unit– whole = sum of the parts!whole = sum of the parts!
mass of 1 molecule of Hmass of 1 molecule of H22O O
= 2(1.01 amu H) + 16.00 amu O = 18.02 amu= 2(1.01 amu H) + 16.00 amu O = 18.02 amu