chapter 5 molecules and compounds (part 2) · chapter 5 molecules and compounds (part 2) 2009,...
TRANSCRIPT
Roy Kennedy
Massachusetts Bay Community College
Wellesley Hills, MA
Introductory Chemistry, 3rd Edition
Nivaldo Tro
Chapter 5
Molecules and
Compounds (Part 2)
2009, Prentice Hall
5.6 Nomenclature: Naming
Compounds
• This will be on quiz 5
Tro's "Introductory Chemistry",
Chapter 5
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Tro's "Introductory Chemistry",
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Formula-to-Name
Step 1
Is the compound one of the
exceptions to the rules?
Tro's "Introductory Chemistry",
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Common Names—Exceptions
• H2O = Water, steam, ice.
• NH3 = Ammonia.
• CH4 = Methane.
• NaCl = Table salt.
• C12H22O11 = Table sugar.
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Formula-to-Name
Step 2
What major class of compound is it?
Ionic or Molecular?
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Classifying Ionic or Molecular• Ionic compounds.
Metal + nonmetal(s) – Binary ionic
Type I cation – charge known
Type II cation – charge must be given
Compounds with polyatomic ions.
• Molecular compounds.
2 or more nonmetals.
Binary molecular (or binary covalent) 2 nonmetals..
Acids—Formula starts with H combined with a anion
either monoatomic or polyatomic ion.
Molecular when pure
Ionic when dissolved in water.
May be binary or oxyacid.
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Formula-to-Name
Step 3
What major subclass of compound is it?
Binary Ionic, Ionic with Polyatomic Ions,
Binary Molecular,
Binary Acid, or Oxyacid?
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Classifying Compounds
• Compounds containing a metal and a nonmetal = Binary ionic.
Type I and II.
• Compounds containing a polyatomic ion = Ionic with polyatomic ion.
• Compounds containing two nonmetals = Binary molecular compounds.
• Compounds containing H and a nonmetal = Binary acids.
• Compounds containing H and a polyatomic ion = Oxyacids.
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Formula-to-Name
Step 4
5.7 Ionic Compounds
5.8 Molecular Compounds
5.9 Acids – Molecular compounds that behave
like ionic compounds in water
5.7 Naming Ionic Compounds
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Types of Ionic Compounds
• Monoatomic cation (metal) and
monoatomic anion (nonmetal)
Cations with only one charge – Type I – Main
group and Ag+ and Zn2+
Cations with more than one charge – Type II –
usually transition metals and some heavier main
group elements
• Polyatomic ion present (KNOW THE
POLYATOMIC IONS FROM THE WEB)Tro's "Introductory Chemistry",
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Formula-to-Name
Rules for Ionic
• Made of cation and anion.
• Name by simply naming the ions.
If cation is:
Type I metal = Metal name.
Type II metal = Metal name (charge).
Polyatomic ion = Name of polyatomic ion.
If anion is:
Nonmetal = Stem of nonmetal name + -ide.
Polyatomic ion = Name of polyatomic ion.
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Monatomic Nonmetal Anion• Charge from periodic table
• To name anion, take the root of the element
name and add the suffix–ide.
• Group 5A Group 6A Group 7A
N3- nitride O2- oxide F- fluoride
P3- phosphide S2- sulfide Cl- chloride
Br- bromide
I- iodide
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Metal Cations• Type I
one possible charge.
1A, 2A, (Al, Zn, Ag).
Charge by position on the periodic table.
1A = +, 2A = 2+, Al = 3+.
Some need to be memorized.
Zn = 2+, Ag = +.
• Type II
Metals whose ions can have more than one possible charge.
Determine charge by charge on anion.
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Type I Binary Ionic Compounds
Formula Cation name Anion name
CaF2 calcium fluoride
K2S potassium sulfide
NaBr sodium bromide
Al2S3 aluminum sulfide
MgO magnesium oxide
Note: no numerical prefixes are used.
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Type II Binary Ionic Compounds
• Cation name (charge as Roman numeral) + anion
name
• Charge is determined from anion
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Determining the Charge on a Variable
Charge Cation—NiCl2 and Fe2S3
1. Ni?+ + 2 Cl-
2. The Ni charge must balance the anions total 2 x (-1) = -2
3. Ni is 2+ nickel(II)chloride
1. Fe2S3 2Fe?+ + 3 S2-
2. The Fe charge balances the anions. 3 x (-2) = =6
3. Fe is 3+, 2 x (+3) = 6 iron(III)sulfide
Another way to work out the
charge• Reverse the method of crossing the charges
Cu2O Cu21+ O 2- copper(I)oxide
Be careful because a common factor may have
been divided out
PbO2 – uncrossing the charges leads to Pb2+ and
O - -, but O is actually O2- . Two O2- is -4
This compound is actuall Pb 4+ lead(IV)oxide
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Tro's "Introductory Chemistry",
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Compounds Containing
Polyatomic Ions
• Name of cation Type I or Type II rules. + name
of anion.
The polyatomic ions you need to
know are on the stuff you must
memorize web page
Stuff you must memorize
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Writing Names for an Ionic Compound Containing
Polyatomic Ion,
Iron(III) phosphate
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Type I
NaNO2 sodium nitrite
Ca(NO3) 2 calcium nitrate
Al2(PO4) 3 aluminum phosphate
Type II
Pb(ClO4) 2 lead(II)perchlorate 2 ClO4- means Pb is 2+
CuSO4 copper (II)sulfate 1 SO42- means Cu is 2+
Fe2(PO4) 3 iron(III) phosphate 2 PO43- means Fe is 3+
5.8 Naming Molecular
Compounds
Tro's "Introductory Chemistry",
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Tro's "Introductory Chemistry",
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Formula-to-Name
Rules for Molecular
• Only for 2 elements binary.
• For binary molecular:
numerical first numerical root
Prefix + element + prefix + second + -ide
(omit if 1) name element
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Numerical Prefixes
• 1 = mono-
Not used on first nonmetal.
• 2 = di-
• 3 = tri-
• 4 = tetra-
• 5 = penta-
• 6 = hexa-
• Drop last ―a‖ if name begins with vowel.
Binary Molecular Compounds
of Two Nonmetals
• SO3 sulfur trioxide
• CS2 carbon dioxide
• S4N4 tetrasulfur tetranitride
• SF6 sulfur hexafluoride
• P2O5 diphosphorus pentaoxide
5.9 Naming Acids
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Formula-to-Name
Acids• Acids have formulas that start with H and contain
an anion either monoatomic or polyatomic
• Acids are molecular, but when dissolved in water they for ions H+ cation(s) and an anion(s).
Binary acids monoatomic ion
• Hydro- prefix + stem of the name of the nonmetal + -ic suffix + acid.
HCl hydrochloric acid
HBr hydrobromic acid
HI hydroiodic acid
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Polyatomic ion acid• Oxyacids:
If polyatomic ion ends in –ate = Name of polyatomic ion with –ic suffix + acid.
If polyatomic ion ends in –ite = Name of polyatomic ion with –ous suffix + acid.
Acid anion name
HNO3 nitrate nitric acid
H2SO3 sulfite sulfurous acid
HClO4 perchlorate perchloric acis
H2CrO4 chromate chromic acid
H3PO4 phosphate phosphoric acid
H3PO3 phosphite phosphorus acid
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Naming compounds from formula
• Decide if common name
• Classify as Ionic or Molecular
• Ionic –
Type I or II cation
Monoatomic or polyatomic ion
• Molecular
Binary
Acids
Binary
OxyacidsTro's "Introductory Chemistry",
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Naming examples
• Ca(ClO4)2 calcium perchlorate
• NH3 ammonia
• P4S5 tetraphosphorous pentasulfide
• HClO3 chlorous acid
• Na2S sodium sulfide
• CoCl3 cobalt(III)chloride
• HBr hydrobromic acid
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5.10 Nomenclature Summary
• An excellent summary of naming
compounds is Figure 5.17 on page 143.
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