1.2 Formal Charges | Organic Chemistry

Chad's Prep
1 Sept 202007:08
EducationalLearning
32 Likes 10 Comments

TLDRThe video script provides a comprehensive lesson on formal charges in organic chemistry, a topic that is often reviewed early in the curriculum. It clarifies that formal charges are distinct from oxidation states and are calculated using a specific formula. The presenter simplifies the formula for easier memorization, suggesting to subtract the 'dots and lines' representing bonds from the normal number of valence electrons. Several examples are given to illustrate the calculation of formal charges for different atoms, such as oxygen, carbon, nitrogen, chlorine, and aluminum, with emphasis on how the typical number of bonds an atom makes affects its formal charge. The video aims to prepare students for organic chemistry exams, where quickly determining formal charges is a crucial skill.

Takeaways
  • 📚 The lesson is about formal charges in organic chemistry, following a review of general chemistry topics like Lewis structures, hybridization, valence bond theory, molecular orbital theory, polarity, and intermolecular forces.
  • 📈 Formal charges are different from oxidation states and are calculated using a specific formula that considers valence electrons, bonding electrons, and non-bonding electrons.
  • ⚖️ The formula for formal charge is the number of valence electrons minus half the number of bonding electrons plus the number of non-bonding electrons.
  • 💡 An easier way to remember the formula is to subtract the total number of dots and lines (single bonds, double bonds, etc.) from the normal number of valence electrons.
  • ➡️ Atoms with a typical number of bonds usually have a formal charge of zero, while those with an abnormal number of bonds often have a non-zero formal charge.
  • 🔵 Carbon typically forms four bonds and has no formal charge, as seen with the carbon atoms in the examples.
  • ⭕ Oxygen typically forms two bonds, but when it forms only one, as in the example, it has a formal charge of -1.
  • 🚫 The formula for calculating formal charge is not favored by the speaker due to its complexity and ease of forgetting.
  • 📝 Assigning formal charges is an essential skill for organic chemistry exams and should be done quickly and accurately.
  • 📚 The speaker recommends using the simplified method of 'normal valence minus dots and lines' for calculating formal charges.
  • 🌟 The lesson is part of a new organic chemistry playlist that will be released weekly during the 2020-2021 school year.
  • 🔔 Subscribers to the channel will receive notifications for each new lesson upload, ensuring they don't miss any content.
Q & A

  • What is the main topic of the second lesson in the organic chemistry playlist?

    -The main topic of the second lesson is formal charges.

  • How does the presenter suggest remembering the formula for calculating formal charges?

    -The presenter suggests remembering the formula by using the phrase 'normal valence minus dots and lines'.

  • What is the difference between formal charges and oxidation states?

    -Formal charges are defined differently than oxidation states. They are not the same thing and are calculated using a specific formula.

  • What is the typical number of bonds a carbon atom makes?

    -A carbon atom typically makes four bonds.

  • Why does the presenter dislike the formal charge formula?

    -The presenter dislikes the formal charge formula because it is hard to remember.

  • What does the presenter mean by 'dots and lines' when referring to the formula for calculating formal charges?

    -In the context of the formula, 'dots and lines' refers to the visual representation of electrons in a Lewis structure, where lines represent shared electrons (bonds) and dots represent non-bonding electrons.

  • What is the normal number of valence electrons for oxygen?

    -The normal number of valence electrons for oxygen is six.

  • How does the presenter simplify the calculation of formal charges for atoms with an abnormal number of bonds?

    -The presenter simplifies the calculation by subtracting the total number of dots and lines from the normal number of valence electrons.

  • What is the typical number of bonds an oxygen atom makes?

    -An oxygen atom typically makes two bonds.

  • Why is it important to be able to assign formal charges quickly in organic chemistry?

    -It is important because the ability to quickly assign formal charges is often required for the first exam in organic chemistry.

  • What is the presenter's recommendation for a resource to practice formal charges and access study guides?

    -The presenter recommends checking out the premium course on chatsprep.com for practice problems involving formal charges and study guides.

  • What is the typical number of bonds an aluminum atom makes according to the octet rule?

    -According to the octet rule, aluminum, being an exception, typically makes three bonds when it has six electrons around it instead of eight.

Outlines
00:00
📚 Introduction to Formal Charges in Organic Chemistry

This paragraph introduces the topic of formal charges within the context of an organic chemistry lesson. The speaker outlines the structure of the course, which includes a review of general chemistry concepts such as Lewis structures, hybridization, valence bond theory, molecular orbital theory, polarity, and intermolecular forces. The focus then shifts to formal charges, emphasizing that they are distinct from oxidation states. A formula for calculating formal charges is presented, using the example of an oxygen atom with one bond, which results in a negative formal charge. The paragraph also discusses the typical bonding behavior of carbon and oxygen, and how deviations from this can lead to formal charges. A simplified method for remembering the formula is suggested, which involves subtracting the dots and lines from the normal number of valence electrons.

05:03
🔍 Assigning Formal Charges to Different Atoms

The second paragraph delves into the process of assigning formal charges to various atoms, using nitrogen, chlorine, and aluminum as examples. It explains that nitrogen, with five valence electrons, typically forms three bonds, but when it forms four, as in the example, it carries a positive formal charge. The paragraph also covers chlorine, which normally forms one bond due to having seven valence electrons. However, aluminum is highlighted as an exception to the octet rule, often forming three bonds with only six electrons. When aluminum forms four bonds, as shown, it results in a negative formal charge. The speaker reiterates the simplified method for calculating formal charges, 'normal valence minus dots and lines,' and encourages quick and accurate assignment of formal charges for success in organic chemistry exams. The paragraph concludes with a call to action for viewers to like, share, and check out the speaker's premium course for further study materials.

Mindmap
Keywords
💡Formal Charges
Formal charges are a method used in chemistry to predict the distribution of electrons in a molecule. They are calculated by taking the number of valence electrons an atom would normally have, subtracting the non-bonding electrons, and then subtracting half the number of electrons in any bonds the atom forms. In the video, formal charges are a central topic, used to explain how atoms in a molecule may carry a charge if they do not form their typical number of bonds. For example, an oxygen atom with one bond instead of the usual two would have a formal charge of -1.
💡Lewis Structures
Lewis structures are diagrams that represent the valence electrons of atoms within a molecule and the bonds they form. They are a fundamental concept in organic chemistry and were discussed in the previous lesson before introducing formal charges. In the script, Lewis structures are mentioned as a prerequisite to understanding formal charges, as they provide the visual representation of the electron distribution that formal charges quantify.
💡Hybridization
Hybridization is a concept in chemistry that describes the mixing of atomic orbitals in a molecule to form new, hybrid orbitals that are suitable for bonding. It is a key topic in understanding molecular geometry and is mentioned in the script as part of the organic chemistry review. The concept is important because it helps explain the different shapes of molecules and how atoms form bonds that are different from their typical valence electron configuration.
💡Valence Bond Theory
Valence bond theory is a method in quantum mechanics that describes the formation of chemical bonds by the overlap of atomic orbitals. It is one of the theories mentioned in the script that helps explain how molecules are held together. The theory is significant for understanding the concept of covalent bonding, which is central to organic chemistry.
💡Molecular Orbital Theory
Molecular orbital theory is a method in chemistry that describes electrons as belonging to molecules rather than individual atoms. It is a more advanced topic that may not be as familiar to students as the other concepts and is mentioned in the script as a part of the curriculum that may not be as much of a review. This theory is important for understanding how electrons are distributed in more complex molecules.
💡Polarity
Polarity refers to the property of a molecule that arises from an uneven distribution of charge, often due to differences in electronegativity between atoms or the shape of the molecule. In the script, polarity is discussed in the context of intermolecular forces and is a key concept for understanding how molecules interact with each other. Polarity can influence many properties of a substance, including its solubility and reactivity.
💡Intermolecular Forces
Intermolecular forces are the forces that act between molecules. They include hydrogen bonding, dipole-dipole interactions, and van der Waals forces. In the video, these forces are mentioned as a topic to be discussed following the explanation of polarity. Understanding these forces is crucial for predicting the physical properties of substances, such as boiling points and solubility.
💡Octet Rule
The octet rule is a principle in chemistry that states that atoms tend to form bonds in such a way that they have eight electrons in their valence shell, achieving a stable electron configuration. However, the script mentions exceptions like boron and aluminum, which often form stable compounds with only six valence electrons. The octet rule is central to understanding the formation of covalent bonds and the structure of molecules.
💡Electronegativity
Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. It is a key factor in determining the polarity of a molecule and is mentioned in the context of intermolecular forces. The difference in electronegativity between atoms in a bond can lead to the formation of polar bonds, which in turn can influence the overall polarity of the molecule.
💡General Chemistry
General chemistry is a foundational course in chemistry that covers basic concepts and principles, including atomic structure, chemical bonding, and the periodic table. In the script, it is mentioned as the starting point for the organic chemistry review, indicating that the audience is expected to have a background in these fundamental topics.
💡Organic Chemistry
Organic chemistry is the study of carbon-containing compounds, their structure, properties, and reactions. The script is part of a new playlist dedicated to organic chemistry, which is a more specialized field of study that builds upon the principles established in general chemistry. The video aims to review and expand upon these principles with a focus on topics like formal charges, which are essential for understanding organic molecules.
Highlights

Lesson focuses on formal charges in organic chemistry, a topic that is a review from general chemistry.

Formal charges are defined differently from oxidation states and are not the same thing.

A formula for calculating formal charges is presented and demonstrated through examples.

Atoms with a normal number of bonds typically have a formal charge of zero.

An alternative, easier method to remember the formal charge formula is introduced.

The presenter dislikes the formal charge formula due to its difficulty to remember.

An example of calculating formal charge for an oxygen atom with one bond is given.

A method of assigning formal charges without using the formal formula is explained.

The presenter suggests counting lines as a single entity rather than half of the electrons in a bond for simplicity.

Carbon atoms making their typical number of bonds will not have a formal charge.

An example of nitrogen making an abnormal number of bonds and having a formal charge is provided.

Chlorine atoms are expected to have one bond and typically do not have a formal charge.

Aluminum is an exception to the octet rule, often having six electrons around them instead of eight.

An aluminum atom with an abnormal number of bonds will have a formal charge.

The importance of being able to quickly assign formal charges for organic chemistry exams is emphasized.

The presenter recommends a method of remembering the formula for formal charge as 'normal valence minus dots and lines'.

The lesson concludes with an invitation to like, share, and check out practice problems and study guides on the presenter's website.

Transcripts

Browse More Related Video

How To Calculate The Formal Charge of an Atom - Chemistry

1.3 Valence Bond Theory and Hybridization | Organic Chemistry

Resonance Structures/Assigning Formal Charge

[H2/H3 Chemistry] Oxidation state & formal charge

What is Resonance -Understanding Orgo Resonance Structures Vid 1 by Leah Fisch

1.1 Lewis Structures | Organic Chemistry Complete Course

Rate This

5.0 / 5 (0 votes)

Thanks for rating:

Related Tags
Organic ChemistryFormal ChargesLewis StructuresHybridizationValence Bond TheoryMolecular Orbital TheoryPolarityIntermolecular ForcesEducational ContentChemistry ReviewSchool YearStudy GuideOnline Learning