Exceptions To The Octet Rule - Lewis Dot Diagrams

TL;DR

Lewis structures can sometimes violate the octet rule, either by having incomplete octets or expanded octets.

Transcript

in this video we're going to go over lewis structures that are exceptions to the octet rule now if you recall the octet rule is that atoms should have eight electrons around it octet means eight the first example that violates the octet rule is bh3 go ahead and draw the lewis structure of bh3 to draw we need to count the number of valence electrons... Read More

Key Insights

• 🍧 Boron trifluoride (BF3) violates the octet rule with an incomplete octet due to having fewer valence electrons.
• 🤨 Second-row elements like carbon, nitrogen, oxygen, and fluorine cannot have expanded octets.
• 🤨 Elements below the second row, such as silicon, phosphorus, sulfur, and chlorine, can have expanded octets.
• 🦕 Lewis structures with odd numbers of electrons will typically violate the octet rule.
• 🫀 Electronegativity influences the stability of Lewis structures, as more electronegative atoms tend to have more electrons in their octets.
• 📏 Lewis structures aim to distribute electrons to achieve stability and fulfill the octet rule.
• #️⃣ The number of valence electrons and the preferred number of bonds for each element can guide the drawing of Lewis structures.

Questions & Answers

Q: Why does boron trifluoride (BF3) violate the octet rule?

Boron only has three valence electrons, and with each hydrogen needing one bond (two electrons), there is no way to fit eight electrons around boron. Thus, it has an incomplete octet.

Q: Can elements in the second row have expanded octets?

No, elements in the second row, like carbon, nitrogen, oxygen, and fluorine, cannot have expanded octets. They can only have incomplete octets.

Q: Which elements can have expanded octets?

Elements below the second row, such as silicon, phosphorus, sulfur, and chlorine, can have expanded octets. They have more than eight electrons around the central atom.

Q: Does every molecule obey the octet rule?

No, not every molecule obeys the octet rule. The octet rule is a general guideline, but there are exceptions where molecules have incomplete or expanded octets.

Summary & Key Takeaways

• Not all molecules follow the octet rule, which states that atoms should have eight electrons around them.

• Boron trifluoride (BF3) is an example of a molecule with an incomplete octet, as boron only has six electrons around it.

• Elements in the second row, like carbon, nitrogen, oxygen, and fluorine, cannot have expanded octets but can have incomplete octets.

• Elements below the second row, such as silicon, phosphorus, sulfur, and chlorine, can have expanded octets.