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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”.

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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”

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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

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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

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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

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chlorous acidClO2 = “chlorite”

Acids, Summary

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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

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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

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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.

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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

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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 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

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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. 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.

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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

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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 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.”

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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)

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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?

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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.

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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

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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

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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)

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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