Ch.9 - Bonding & Molecular StructureSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Sections
Chemical Bonds
Lattice Energy
Lattice Energy Application
Born Haber Cycle
Dipole Moment
Lewis Dot Structure
Octet Rule
Formal Charge
Resonance Structures
Additional Practice
Bond Energy

The Octet Rule states that main-group elements will generally form enough bonds to obtain 8 electrons in their valence shell. 

Incomplete Octets

Concept #1: Understanding Incomplete Octets

An incomplete octet occurs when the central element in a Lewis Dot Structure is surrounded by less than 8 valence electrons. 

Example #1: Draw the following molecular compound. 

BH3

Practice: Draw the following molecular compound. BeCl2

Note: Assume all Cl atoms already have electrons. 

Expanded Octets

Concept #2: Understanding Expanded Octets

An expanded octet occurs when the central element in a Lewis Dot Structure is surrounded by more than 8 valence electrons. 

Example #2: Draw each of the following molecular compounds. 

IF3                                                

Example #3: Draw each of the following molecular compounds. 

KrF5+                                                

Practice: Draw the following molecular compound. SBr4

Note: Assume all Br atoms already have electrons. 

Practice: Draw the following molecular compound, the triiodide ion, I3-.

Drawing Polyatomic Ions

Concept #3: Shortcut to Drawing Polyatomic Ions 

Example #4: Draw the following molecular compound.

SO42-

Example #5: Draw the following molecular compound.

PO4­3–     

Example #6: Draw the following molecular compound.

H2SO4  

Practice: Draw the following molecular compound. SeO42-

Practice: Draw the following molecular compound.

XeO64-

Additional Problems
Write a Lewis structure for each of the following molecules that are exceptions to the octet rule.BCl3
Write a Lewis structure for each of the following molecules that are exceptions to the octet rule.NO2
Write a Lewis structure for each of the following molecules that are exceptions to the octet rule.BH3
Write Lewis structures for each of the following species. Use expanded octets as necessary.PF5
Write Lewis structures for each of the following species. Use expanded octets as necessary.SF4
Write Lewis structures for each of the following species. Use expanded octets as necessary.GeF4
Some theories of aging suggest that free radicals cause certain diseases and perhaps aging in general. As you know from Lewis theory, such molecules are not chemically stable and will quickly react with other molecules. Free radicals may attack molecules within the cell, such as DNA, changing them and causing cancer or other diseases. Free radicals may also attack molecules on the surfaces of cells, making them appear foreign to the bodys immune system. The immune system then attacks the cells and destroys them, weakening the body. Draw Lewis structures for each of the following free radicals implicated in this theory of aging.OH
You may want to reference (Pages 300 - 301) Section 8.1 while completing this problem.True or false: The hydrogen atom is most stable when it has a full octet of electrons.
The standard state of phosphorus at 25oC is P4. This molecule has four equivalent P atoms, no double or triple bonds, and no expanded octets. Draw its Lewis structure.
Why does the octet rule have exceptions?
List the three major categories of exceptions and an example of each.
Which elements can have expanded octets?
Which elements should never have expanded octets?
Although I3- is known, F3- is not.One of your classmates says F3- does not exist because it would violate the octet rule. Is this classmate possibly correct?
Draw the dominant Lewis structures for these chlorine-oxygen molecules/ions.Which of these do not obey the octet rule?
For elements in the third row of the periodic table and beyond, the octet rule is often not obeyed. A friend of yours says this is because these heavier elements are more likely to make double or triple bonds. Another friend of yours says that this is because the heavier elements are larger and can make bonds to more than four atoms at a time.Which friend is most correct?
Which compounds violate the octet rule? (Be sure to draw all the structures before you decide!)NO2     CH2Cl2     XeF4     NCl3a. NO2 and XeF4b. NO2 and CH2Cl2c. CH2Cl2 and NCl3d. XeF4 and NCl3
In which one of the following compounds can a valid Lewis structure be drawn but it is permissible for the central atom to violate the octet rule?a. NF3b. IF3c. PF3d. SbF3e. CO2
What is the lewis structure for SeOBr 2?
Draw a Lewis structure for SiCl4 and answer the following questions based on your drawing.1. For the central silicon atom:The number of lone pairs=The number of single bonds=The number of double bonds=2. The central silicon atom _________obeys the octet rule.has an incomplete octet.has an expanded octet.
Which of the following molecules does NOT contain an exception to the octet rule?A. SF4B. NOC. BH3D. XeF2E. N2O
Consider the following set of molecules:I). BF3      II). CHBr3 (central atom is C)     III). Br2      IV). XeCl2       V). CO      VI). SF4Select the group that best fits the following statement: These molecules violate the octet rule.a) I, III, IV, VIb) I, IV, VIc) I, II, IVd) III, V, VIe) I, II, IV, VI
Which of the following species is a radical?CH2OHCNHClOClONO2ClO
Consider the following moleculesI. BCl3        II. CHBr3 (C is the central atom)      III. Cl2        IV. XeBr2          V. COThese molecules do not follow the octet rule.I, IVI, III, IV, VIIII, V, VII, IV, VII, II, IV, VI
Which of the following contains an atom that does not obey the octet rule?a. KBrb. CO2c. ClF3d. ICl
Which of the following elements can form compounds with an expanded octet (doesn't obey octet)?a) Seb) Cc) Lid) Fe) B
Draw the Lewis structure of ClO 2 with minimized formal charge. Which atom does not have 8 valence electrons.
Write a Lewis structure for each of the following molecules that are exceptions to the octet rule.BBr3       NO     ClO2    
Molecules of which compounds violate the octet rule?a) 1 and 2b) 1 and 3c) 2 and 3d) 2 and 4
Which of the species NO, BrO, CH3+, BF4– are radicals?1. NO and BrO only2. BrO and CH3+ only3. BrO and BF4+ only4. NO, CH3+ and BF4– only5. NO and CH3+ only6. BrO, CH3+ and  BF4– only7. NO and BF4– only
Which of the following atoms can expand its valence shell when bonding?a. Pb. Cc. Ald. Ne. O
Which is an isomer of the structure that is given in the box below?
Which of these satisfy the octet rule and which do not? Drag the appropriate items to their respective bins.
Which of the following statements is/are true?i. B in BF3 violates the octet ruleii. Xe in XeF2 violates the octet ruleiii. S in SF2 violates the octet rule.a. i onlyb. iii onlyc. i and iid. i and iiie. ii and iii
Which of the following atoms can expand its valence shell? (Select all that apply.)S, Al, F, H, Cl, Se
Which molecule could have an expanded octet?a. H2CO3b. H3PO4c. HNO2
How many lone pairs are on the central atom in BrF3? Express your answer numerically as an integer.
Which of the following elements can form compounds with an expanded octet?a. Nb. Brc. Fd. Bee. None of the above
If the boron nitride molecule, BN , were to form, what would its structure look like?
One type of exception to the octet rule are compounds with central atoms having fewer than eight electrons around them. BeH2 and BH3 are examples of this type of exception. Draw the Lewis structures for BeH2 and BH3.
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:(a) BH3 
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception: (b) AsF4 −
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception: (c) SeCl4
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:(a) PF6−
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:(b) ClO3 
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:(c) H3PO3 (one P—H bond)
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:(a) BrF3
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:(b) ICl2−
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:(c) BeF2
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:(a) O3−
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:(b) XeF2
These species do not obey the octet rule. Draw a Lewis structure for each, and state the type of octet-rule exception:(c) SbF4−
The most common exceptions to the octet rule are compounds or ions with central atoms having more than eight electrons around them. PF5, SF4, ClF3, and Br3- are examples of this type of exception. Draw the Lewis structure for these compounds or ions. Which elements, when they have to, can have more than eight electrons around them? How is this rationalized?
SF6, ClF5, and XeF4 are three compounds whose central atoms do not follow the octet rule. Draw Lewis structures for these compounds.
Some theories of aging suggest that free radicals cause certain diseases and perhaps aging in general. As you know from Lewis theory, such molecules are not chemically stable and will quickly react with other molecules. Free radicals may attack molecules within the cell, such as DNA, changing them and causing cancer or other diseases. Free radicals may also attack molecules on the surfaces of cells, making them appear foreign to the bodys immune system. The immune system then attacks the cells and destroys them, weakening the body. Draw Lewis structures for each of the following free radicals implicated in this theory of aging.CH3OO (unpaired electron on terminal oxygen)
Free radicals are important in many environmentally significant reactions (see the Chemistry in the Environment box on free radicals in Chapter 9 in the textbook). For example, photochemical smog (smog that results from the action of sunlight on air pollutants) forms in part by these two steps:NO2 + UV light → NO + OO + O2 → O3The product of this reaction, ozone, is a pollutant in the lower atmosphere. (Upper atmospheric ozone is a natural part of the atmosphere that protects life on Earth from ultraviolet light.) Ozone is an eye and lung irritant and also accelerates the weathering of rubber products. Which of these species are free radicals?
You may want to reference (Pages 382 - 416) Chapter 9 while completing this problem.Free radicals are important in many environmentally significant reactions (see the Chemistry in the Environment box on free radicals in Chapter 9 in the textbook). For example, photochemical smog (smog that results from the action of sunlight on air pollutants) forms in part by these two steps:NO2 + UV light → NO + OO + O2 → O3The product of this reaction, ozone, is a pollutant in the lower atmosphere. (Upper atmospheric ozone is a natural part of the atmosphere that protects life on Earth from ultraviolet light.) Ozone is an eye and lung irritant and also accelerates the weathering of rubber products. Construct the Lewis structure of NO.
You may want to reference (Pages 382 - 416) Chapter 9 while completing this problem.Free radicals are important in many environmentally significant reactions (see the Chemistry in the Environment box on free radicals in Chapter 9 in the textbook). For example, photochemical smog (smog that results from the action of sunlight on air pollutants) forms in part by these two steps:NO2 + UV light → NO + OO + O2 → O3The product of this reaction, ozone, is a pollutant in the lower atmosphere. (Upper atmospheric ozone is a natural part of the atmosphere that protects life on Earth from ultraviolet light.) Ozone is an eye and lung irritant and also accelerates the weathering of rubber products. Construct the Lewis structure of O.
A major short-lived, neutral species in flames is OH.(a) What is unusual about the electronic structure of OH?
You may want to reference (Pages 408 - 411)Section 9.9 while completing this problem.Write a Lewis structure for each of the following molecules that are exceptions to the octet rule.BBr3
You may want to reference (Pages 408 - 411)Section 9.9 while completing this problem.Write a Lewis structure for each of the following molecules that are exceptions to the octet rule.NO
You may want to reference (Pages 408 - 411)Section 9.9 while completing this problem.Write a Lewis structure for each of the following molecules that are exceptions to the octet rule.ClO2
Draw the lewis structure fora. CH4Sb. S2Cl2 c. CHCl3
Draw the Lewis structure for HCN molecule. Include lone pairs.
Draw the Lewis structure of the hypochlorite ion, ClO -. Include lone pairs.
Complete these structures by adding dots as needed.
Draw a Lewis structure for NHF2 in which the central N atom obeys the octet rule, and answer the following questions based on your drawing. The number of unshared pairs (lone pairs) on the central N atom is: _____The central N atom forms _____ single bonds. The central N atom forms _____ double bonds.
Draw a Lewis structure for CO32- in which the central C atom obeys the octet rule, and answer the following questions based on your drawing. The number of unshared pairs (lone pairs) on the central C atom is: _____The central C atom forms _____ single bonds. The central C atom forms _____ double bonds.
Consider the following four molecules: CO2-3, PF5, CS2, BBr3.Which of these satisfy the octet rule and which do not?