Lewis Structures and Expanded Octets

This video tutorial explains the concept of expanded octets in molecules, focusing on elements in the third period and below, such as phosphorus and sulfur, which can have expanded octets due to available D orbitals. The video provides a detailed example using the sulfate ion, demonstrating how to draw its Lewis structure and calculate formal charges to determine the need for an expanded octet. It also discusses other examples like phosphorus pentachloride and SF6, highlighting when expanded octets are necessary.

Which period of the periodic table is primarily associated with elements that can have expanded octets?

• First period

• Second period

• Fourth period

• Third period

What allows elements like phosphorus and sulfur to have expanded octets?

• Presence of f orbitals

• Presence of d orbitals

• Presence of p orbitals

• Presence of s orbitals

Which of the following elements is most likely to form an expanded octet?

• Oxygen

• Sulfur

• Nitrogen

• Carbon

In the sulfate ion, what is the formal charge on an oxygen atom with a single bond?

• +1

• 0

• -1

• -2

What is the charge on the sulfate ion?

• 1-

• 2-

• 3-

• 4-

Why is it important to check formal charges when drawing Lewis structures?

• To determine the molecular weight

• To calculate the number of atoms

• To ensure the structure is symmetrical

• To find the most stable structure

What is the formal charge on a double-bonded oxygen in a sulfate ion?

• +1

• 0

• -1

• -2

What is the significance of achieving zero formal charges in a Lewis structure?

• It means the molecule is aromatic

• It suggests a more stable structure

• It shows the molecule is an ion

• It indicates a non-polar molecule

Which molecule is an example of one that requires an expanded octet?

• SF6

• CO2

• H2O

• NH3

How many valence electrons are around phosphorus in phosphorus pentachloride?

• 14

• 12

• 10

• 8