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LecturePLUS Timberlake 1
ChemIH: Chapters 8 & 9Covalent Bonding
Def: bonds btwn 2 nonmetals
Nonmetals have high EN values so electrons must be shared
Compounds w/covalent bonds are called molecular compounds.
Covalent Bonding
• single bond shares 1 pair electrons- ex:H2
• double bond shares 2 pairs electron-ex:O2
• triple bond shares 3 pairs electrons-ex: N2
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Covalent Bonding
• By sharing e-s, atoms obtain NGC, which makes them more stable than they were by themselves.
H + H H : H = HH = H2
hydrogen molecule
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Learning Check
Indicate whether a bond between the following would be
(I) Ionic OR (C) covalent
____ A. sodium & oxygen
____ B. nitrogen & oxygen
____ C. phosphorus & chlorine
____ D. calcium & sulfur
____E. chlorine & bromine
LecturePLUS Timberlake 5
Solution
Indicate whether a bond between the following would be
(I) Ionic OR (C) covalent
I A. sodium and oxygen
C B. nitrogen and oxygen
C C. phosphorus and chlorine
I D. calcium and sulfur
C E. chlorine and bromine
There are 3 types of molecular substances we will learn about.
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1. Diatomic Elements
• Elements that exist as atom pairs
: H2, O2, N2, Cl2, Br2, I2, F2,
• They are given the name of the element.
octets
N +
N N:::N triple bond
LecturePLUS Timberlake 8
Learning Check
Use the name of the element to name a
diatomic molecules.
H2 hydrogen
N2 nitrogen
Cl2 _______________
O2 _______________
I2 _______________
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Solution
Use the name of the element to name the
following diatomic molecules.
H2 hydrogen
N2 nitrogen
Cl2 chlorine
O2 oxygen
I2 iodine
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2. Binary Covalent Compounds
• Two nonmetals (def of binary covalent)1. Name each element
2. End the last element in -ide
3. Add prefixes to show how many atoms of each(except when there’s only 1 atom of the 1st element listed)
PREFIXES
mono- 1 penta- 5di- 2 hexa- 6tri - 3 hepta- 7tetra- 4 octa- 8
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Learning Check
Fill in the blanks to complete the following names of covalent compounds.
CO carbon ______oxide
CO2 carbon _______________
PCl3 phosphorus _______chloride
CCl4 carbon ________chloride
N2O _____nitrogen _____oxide
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Solution
CO carbon monoxide
CO2 carbon dioxide
PCl3 phosphorus trichloride
CCl4 carbon tetrachloride
N2O dinitrogen monoxide
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Learning Check
A. P2O5 1) phosphorus oxide2) phosphorus pentoxide3) diphosphorus pentoxide
B. Cl2O7 1) dichlorine heptoxide2) dichlorine oxide3) chlorine heptoxide
C. Cl2 1) chlorine2) dichlorine3) dichloride
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Solution
A. P2O5 3) diphosphorus pentoxide
B. Cl2O7 1) dichlorine heptoxide
C. Cl2 1) chlorine
3. Organic Compounds• Def: organic compounds contain
carbon atoms hooked together.
• (Why do you think this element can hook up with many other atoms, including itself?)
Hydrocarbons-A Type of Organic Compound
• Def: hydrocarbons are made of hydrogen & carbon
• They are named by the number of carbon atoms a molecule contains.
• They are important as fuels.
Hydrocarbons • The table below lists only hydrocarbons
w/single bonds\• The names all end w/ “ane”
CH4 methane C6H14 hexane
C2H6 ethane C7H16 heptane
C3H8 propane C8H18 octane
C4H10 butane C9H20 nonane
C5H12 pentane C10H22 decane
Writing Formulas for Molecular Compounds
1. Analyze the name of the compound
2. Identify the type of compound (diatomic? binary? hydrocarbon?)
3. Reverse the process used to name it so you can determine the formula. (For binary, prefixes indicate the subscript.)
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Common v. Formal Names
• Formal Names follow the rules we have learned for naming compounds.
• Common Names are ones that don’t follow these rules.
–Ex: water=
Frequently Used Common Names
• Water = H2O
• Ammonia = NH3
MOLECULE
• Def: unit formed when elements combine via covalent bonding
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Covalent Bonds in NH3
Bonding pairs
H
H : N : H
Lone pair of electrons
Allotropes• Def: molecules of the same element that differ in
structure
• Ex 1: Carbon…graphite, charcoal, Buckminsterfullerine (“bucky ball”)=
C64
• Ex 2: O2 (oxygen) and O3 (ozone)
Q:Why do we have to specify the number of atoms of each element in
a covalent compound?
A: Atoms of the same elements can combine in different ratios.
• Ex: C & OCOCO2
Writing Formulas for Covalent Compounds
1. Identify it as a covalent: containing only nonmetals.
2. Determine what type of covalent it is:
diatomic element binary
hydrocarbon (ends in –ane) acid/base
3. Reverse the naming process.
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STOP HERE!!!
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Naming Ionic Compounds•Binary Ionic
• Ionic Compounds contain-ing Polyatomic Ions.
• Ionic Cpds containing Transition Metals
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PLEASE NOTE:• IF YOU ARE UNABLE TO
IDENTIFY IONIC & COVALENT COMPOUNDS, YOU WILL BE LOST!!!
• PLEASE SEE ME IMMEDIATELY TO GET CAUGHT UP.
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Ionic Bonding & Electronegativity
Nonmetals have high EN’s. Metals have low EN’s.
Bonds between a metal & a nonmetal involve transfers of e-s b/c of the big difference in EN!
Binary Ionic Compounds
•Binary= 2 elements
•Ionic= 1 metal & 1 nonmetal
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Naming Binary Ionic Compounds1. Identify & name the 2 elements in the
compound.
2. Name the cation, which is the given the name of the element.
3. Name the anion, which is given the name of the element, w/the ending changed to “–ide.”
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PRACTICE Naming Binary Ionic Compounds
1. Na║Cl
2. Na = “sodium”
3. Cl = “chloride”(full name is “sodium chloride”)
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PRACTICE Naming Binary Ionic Compounds
1. Li2O
2 & 3.
____║____= ______ ______ (cation (anion (cation name) (anion name)
symbol) symbol)
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MORE PRACTICE Naming Binary Ionic Compounds-p __ of I.N.
1. KF
2. CaF2
3. Al2O3
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Naming Ionic Compounds w/ Polyatomic Ions
• DEF: Charged particles containing more than 1 type of atom. Ex: SO4
2-
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Naming Ionic Compounds w/ Polyatomic Ions
1. Identify the cation & the anion. (Draw a line between the 2 ions)
2. Name the cation, then the anion (find polyatomics on Table 5.3, p 159 of text). That’s it!
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PRACTICE :Naming Ionic Compounds w/ Polyatomic Ions
EX: Na2SO4
____║____= ______ ______ (cation (anion (cation name) (anion name)
symbol) symbol)
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Naming Ionic Compounds w/ Polyatomic Ions
• Most polyatomic ions are anions.
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A Couple of Important Exceptions w/Polyatomic Ions
Important Exception #1: there are 2 cations that contain NO METALS:
NH4+ (ammonium)
H3O+ (hydronium)
(this can be tricky b/c we have always identified ionic compounds because they start with a metal cation.)
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A Couple of Important Exceptions w/Polyatomic Ions
Important Exception #2: Some anions contain metals.
Ex: MnO4- = permanganate
Cr2O72- = dichromate
(this can be tricky b/c anions are usually a nonmetal)
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Copy Table 5.2 into Notes
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Naming Ionic Cpds Containing Transition MetalsEx: NiO2
1.Determine the total # of negative charges in a unit of the compound:
Ex: O2- & O2- = 4 total - charges
2. Determine the charge on the cation that will give you 4 total + charges Ex: Ni4+
3. Write the cation & anion names. Write cation with the oxidation # written as a Roman numeral in parentheses:
Ex: nickel (IV) oxide
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Writing Formulas for Binary Ionic Compounds
1. Identify the ionic charge (“oxidation number”) on the cation & anion.
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Writing Formulas for Binary Ionic Compounds
ELEMENT OXIDATION #• Group 1 1+• Group 2 2+• Group 13 3+• Group 14 4+ or 4-• Group 15 3-• Group 16 2-• Group 17 1-
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Practice Predicting Oxidation #s
• Li
• O
• Mg
• F
• B
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Writing Formulas for Binary Ionic Compounds
2. A compound has NO CHARGE on it, so a formula unit (the smallest ratio of cations to anions) must have equal numbers of + & - charges. (use the LCM)
LecturePLUS Timberlake 47
Cross-Over Method• You can use this to write formulas.
• Take the charge on the cation and use it as the subscript on the anion
• Take the charge on the anion and use it as the subscript on the cation
• Reduce the subscripts, if necessary
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Using the LCM to Write Ionic Formulas
• Ex: Li & F
• Ex: Li & O
• Ex: Al & O
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ANSWERS
• LiF
• Li2O
• Al2O3
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Writing Formulas for I.Cpds Containing Polyatomic Ions
• Determine the cation & anion• Determine the oxidation # on each ion.
(oxidation #s for polyatomics are found on Table 5.2)
• Write a balanced formula–If there is more than 1 of an ion, use
parentheses, then a subscript
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Writing Formulas for I.Cpds Containing Polyatomic Ions
• Ex: see Practice Problems, p 162
3. Write the formula for the compound formed from the following pairs of ions
a) ammonium & sulfite ions
• IONS: NH4+
& SO3 2-
NH4+
• FORMULA: (NH4)2SO3
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Practice Problems, cont.from p 16 2of text
3b)
3c)
3d)
4a)
4b)
4c)
4d)
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Transition Metals• QUESTION: What was strange about the
e- configurations of transition metals?
LecturePLUS Timberlake 54
ANSWER: Their d sublevels overlap with the other sublevels in the next higher main E.L.
Oxidation #s of Transition Metals
• The d sublevel e-s are so close to the actual valence e-s, they sometimes act like valence e-s!
• See Table 5.4 on p 164 of text: Common Ions of Select Transition Metals
• Ex: Fe 2+ & Fe 3+
• Write the e- configuration
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e- Configuration for Fe• Fe=26 e-s• 1s22s22p63s23p64s23d6
• Valence e-s=4s2
• BUT, some 3d e-s can be lost too!
• NOTE: Students found this a bit confusing, or at best minimally
helpful. Explain, but do not belabor the e- config.
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Writing Formulas for Ionic Cpds containing Transition Metals
1. Identify the cation & anion
2. Determine the oxidation #s on the cation & anion
–The oxidation # of the cation is given in the name ex: Nickel (IV) = Ni4+
–The Roman numeral is the oxidation#
3. Write a formula w/ 0 charge.
LecturePLUS Timberlake 57
Distillation• Def: process of separating ionic &
covalent compounds by heating them till the covalent compound evaporates.– The ionic compound remains in the
flask– The covalent compound can be cooled
& collected in a separate container.– This process is called distillation
LecturePLUS Timberlake 59
Learning Check
Match each set with the correct name:
A. Na2CO3 1) magnesium sulfite
MgSO3 2) magnesium sulfate
MgSO4 3) sodium carbonate
B. Ca(HCO3)2 1) calcium carbonate
CaCO3 2) calcium phosphate
Ca3(PO4)2 3) calcium bicarbonate
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Solution
A. Na2CO3 3) sodium carbonate
MgSO3 1) magnesium sulfite
MgSO4 2) magnesium sulfate
B. Ca(HCO3)2 3) calcium bicarbonate
CaCO3 1) calcium carbonate
Ca3(PO4)2 2) calcium phosphate
LecturePLUS Timberlake 61
Learning Check
A. aluminum nitrate
1) AlNO3 2) Al(NO)3 3) Al(NO3)3
B. copper(II) nitrate
1) CuNO3 2) Cu(NO3)23) Cu2(NO3)
C. Iron (III) hydroxide
1) FeOH 2) Fe3OH 3) Fe(OH)3
D. Tin(IV) hydroxide
1) Sn(OH)4 2) Sn(OH)2 3) Sn4(OH)
LecturePLUS Timberlake 62
Solution
A. aluminum nitrate
3) Al(NO3)3
B. copper(II) nitrate
2) Cu(NO3)2
C. Iron (III) hydroxide
3) Fe(OH)3
D. Tin(IV) hydroxide
1) Sn(OH)4
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