Ch.9 - Bonding & Molecular StructureWorksheetSee 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

Transcript

We say that nonmetals form covalent bonds. Covalent bonds have the sharing of electrons between different nonmetals or the same nonmetals. We're going to say, generally, they follow the octet rule. The octet rule is when the element is surrounded by eight valence electrons, the central element in our compound. This isn't always the case. Sometimes we can have the central element having less than eight valence electrons around it or more than eight valence electrons around it.
We're going to say sometimes elements form compounds in which they have less than eight valence electrons. When they make less than eight valence electrons around them, they're called incomplete octets or they are electron deficient. Just remember, electron deficient is the same thing as having an incomplete. Meaning you have less than eight valence electrons around you.

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

Transcript

Remember, we say that covalent bonds are the connections between non-metals, they tend to share electrons with one another in order to achieve the octet rule where the central element has 8 valence electrons around it. But remember, certain elements can have less than 8 or more than 8 electrons. When we talk about the expanded octet, we mean that the central element will have more than 8 electrons around it. Now we're going to say nonmetals starting from period 3 to period 7 can have more than 8 valence electrons around them when in the center. 

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 

Transcript

When it comes to drawing Lewis dot structures, polyatomic ions are considered some of the hardest types to draw. The good thing is from all the years of looking at different structures, I've noticed a pattern. From this pattern, I've come up with a shortcut. We’re going to use this shortcut anytime we have to draw complex polyatomic ion. The good thing is it covers a majority of the polyatomic ions that you’re used to seeing.
We're going to say if you have carbon, sulfur, selenium, phosphorus, halogen, or a noble gas and they're connected to oxygen. One of these guys will be connected to oxygen. Then the negative charge tells you how many oxygens are single bonded. The remaining oxygens will be double bonded to the central element.
What the heck does that mean? Let's take a look at the first example and you'll see what I mean by this shortcut.

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-