LecturePLUS Timberlake1 ChemIH: Chapters 6 & 7 Covalent Bonding Def: bonds btwn 2 or more nonmetals...
-
Upload
cecilia-lewis -
Category
Documents
-
view
227 -
download
0
Transcript of LecturePLUS Timberlake1 ChemIH: Chapters 6 & 7 Covalent Bonding Def: bonds btwn 2 or more nonmetals...
LecturePLUS Timberlake 1
ChemIH: Chapters 6 & 7 Covalent Bonding
Def: bonds btwn 2 or more nonmetals
Nonmetals have high EN values so electrons must be shared
Compounds w/covalent bonds are called molecular compounds.
We will learn about 4 types of molecular cpds.
1. Acids
• Acids are covalent compounds that act like ionic compounds.
• They have H+ as the “cation”.
LecturePLUS Timberlake 2
Acids
• There are 3 types of acids.
• They are named based on the type of ANION they contain:
1.Anion = element
2.Anion = polyatomic ion that ends in “ate”
3.Anion = polyatomic ion that ends in “ite”
LecturePLUS Timberlake 3
Acids
1. If anion is an element, name of acid is “hydro____ic acid” where blank is filled with root of element name
• Ex: HCl
LecturePLUS Timberlake 4
Hydrochloric acid
Acids
2. If anion is a polyatomic ion that ends in
“-ate”, name of acid is “____ic acid” where blank is filled with root of polyatomic ion name
• Ex: HClO3
LecturePLUS Timberlake 5
chloric acidClO3 = “chlorate”
Acids
3. If anion is a polyatomic ion that ends in
“-ite”, name of acid is “____ous acid” where blank is filled with root of element name
• Ex: HClO2
LecturePLUS Timberlake 6
chlorous acidClO2 = “chlorite”
Acids, Summary
LecturePLUS Timberlake 7
Type of Anion
Naming rule Example
Element Hydro___ic acid HCl: hydrochloric acid
Polyatomic “-ate”
____ic acid HClO4: perchloric acid
Polyatomic “-ite”
____ous acid HClO: hypochlorous acid
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
LecturePLUS Timberlake 8
LecturePLUS Timberlake 9
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
LecturePLUS Timberlake 10
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 11
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 4 types of molecular substances we will learn about.
LecturePLUS Timberlake 12
LecturePLUS Timberlake 13
2. 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 14
Learning Check
Use the name of the element to name a
diatomic molecules.
H2 hydrogen
N2 nitrogen
Cl2 _______________
O2 _______________
I2 _______________
LecturePLUS Timberlake 15
Solution
Use the name of the element to name the
following diatomic molecules.
H2 hydrogen
N2 nitrogen
Cl2 chlorine
O2 oxygen
I2 iodine
LecturePLUS Timberlake 16
2. Binary Covalent CompoundsTwo nonmetals (def of binary covalent)1.Name each element 2.End the last element in -ide3.Add prefixes to show how many atoms of each
(except when there’s only 1 atom of the 1st element listed)
PREFIXESmono 1 hexa 6di 2 hepta7tri 3 octa 8tetra 4 nona 9penta 5 deca 10
LecturePLUS Timberlake 17
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
LecturePLUS Timberlake 18
Solution
CO carbon monoxide
CO2 carbon dioxide
PCl3 phosphorus trichloride
CCl4 carbon tetrachloride
N2O dinitrogen monoxide
LecturePLUS Timberlake 19
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
LecturePLUS Timberlake 20
Solution
A. P2O5 3) diphosphorus pentoxide
B. Cl2O7 1) dichlorine heptoxide
C. Cl2 1) chlorine
3. Hydrocarbons-A Type of Binary Covalent 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.
LecturePLUS Timberlake 23
Tips for Identifying TYPE of Molecular Compound
IF THE NAME HAS: TYPE OF COMPOUND HOW TO WRITE
FORMULA
• Just the name of 1of • Diatomic Element • H2, O2, N2, Cl2,
the following elements: Br2, I2, F2
(HONClBrIF)
• Prefixes • Binary (2 elements) • Turn prefixes into
• Ends in “-ide” subscripts. (Write them after element symbol)
• Ends in “-ane” • Hydrocarbon • Look it up on list of hydrocarbons!LecturePLUS Timberlake 24
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
LecturePLUS Timberlake 27
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.
LecturePLUS Timberlake 30
STOP HERE!!!
LecturePLUS Timberlake 31
Naming Ionic Compounds•Binary Ionic
• Ionic Compounds contain-ing Polyatomic Ions.
• Ionic Cpds containing Transition Metals
LecturePLUS Timberlake 32
PLEASE NOTE:• IF YOU ARE UNABLE TO
IDENTIFY IONIC & COVALENT COMPOUNDS, YOU WILL BE LOST!!!
• PLEASE SEE ME IMMEDIATELY TO GET CAUGHT UP.
LecturePLUS Timberlake 33
LecturePLUS Timberlake 34
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
LecturePLUS Timberlake 35
Naming Binary Ionic Compounds
1. Name the cation, which is the given the name of the element.
2. Name the anion, which is given the name of the element, w/the ending changed to “–ide.”
LecturePLUS Timberlake 36
PRACTICE Naming Binary Ionic Compounds
1. Na║Cl
2. Na = “sodium”
3. Cl = “chloride”(full name is “sodium chloride”)
LecturePLUS Timberlake 37
PRACTICE Naming Binary Ionic Compounds
1. Li2O
2 & 3.
____║____= ______ ______ (cation (anion (cation name) (anion name)
symbol) symbol)
LecturePLUS Timberlake 38
MORE PRACTICE Naming Binary Ionic Compounds-p __ of I.N.
1. KF
2. CaF2
3. Al2O3
LecturePLUS Timberlake 39
Naming Ionic Compounds w/ Polyatomic Ions
• DEF: Charged particles containing more than 1 type of atom. Ex: SO4
2-
LecturePLUS Timberlake 40
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!
LecturePLUS Timberlake 41
PRACTICE :Naming Ionic Compounds w/ Polyatomic Ions
EX: Na2SO4
____║____= ______ ______ (cation (anion (cation name) (anion name)
symbol) symbol)
LecturePLUS Timberlake 42
Naming Ionic Compounds w/ Polyatomic Ions
• Most polyatomic ions are anions.
LecturePLUS Timberlake 43
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.)
LecturePLUS Timberlake 44
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)
LecturePLUS Timberlake 45
Copy Table 5.2 into Notes
LecturePLUS Timberlake 46
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
LecturePLUS Timberlake 47
Writing Formulas for Binary Ionic Compounds
1. Identify the ionic charge (“oxidation number”) on the cation & anion.
LecturePLUS Timberlake 48
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-
LecturePLUS Timberlake 49
Practice Predicting Oxidation #s
• Li
• O
• Mg
• F
• B
LecturePLUS Timberlake 50
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 51
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
LecturePLUS Timberlake 52
Using the LCM to Write Ionic Formulas
• Ex: Li & F
• Ex: Li & O
• Ex: Al & O
LecturePLUS Timberlake 53
ANSWERS
• LiF
• Li2O
• Al2O3
LecturePLUS Timberlake 54
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
LecturePLUS Timberlake 55
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
LecturePLUS Timberlake 56
Practice Problems, cont.from p 16 2of text
3b)
3c)
3d)
4a)
4b)
4c)
4d)
LecturePLUS Timberlake 57
Transition Metals• QUESTION: What was strange about the
e- configurations of transition metals?
LecturePLUS Timberlake 58
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
LecturePLUS Timberlake 59
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.
LecturePLUS Timberlake 60
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 61
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 63
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
LecturePLUS Timberlake 64
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 65
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 66
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