Ligação Covalente - Brasil Escola

Brasil Escola Oficial

17 Jan 201910:35

Summary

TLDRIn today's chemistry lesson, the focus is on covalent bonding, contrasting with ionic bonds. Covalent bonds, as explained, involve electron sharing between atoms, unlike ionic bonds which are characterized by electron transfer. The video uses the example of Cl2 to illustrate how atoms share electrons to achieve stability, following the octet rule. It simplifies the concept with a game lending analogy and discusses different types of covalent bonds, such as single, double, and triple bonds. The lesson also covers molecular formulas, electronic formulas, and structural formulas. An exercise from the ENEM (Brazilian college entrance exam) is used to apply these concepts, focusing on molecules with expanded octets. The video concludes with an invitation to engage with the content and explore further topics.

Takeaways

🔬 Covalent bonds are based on the sharing of electron pairs between atoms, differing from ionic bonds which involve the transfer of electrons.
📚 The term 'covalence' refers to the sharing of electrons, which is fundamental to covalent bonding.
🧩 In a covalent bond, atoms with a tendency to gain electrons share electron pairs to achieve stability, following the octet rule.
🌐 An example given is Cl2, where each chlorine atom shares one electron to complete its valence shell, resulting in a double bond between the two chlorine atoms.
🎮 A relatable analogy is borrowing a video game from a friend while lending one of yours, symbolizing the mutual sharing in covalent bonds.
🔗 Covalent bonds can be single, double, or triple, depending on the number of electron pairs shared between atoms.
📐 The script explains that covalent bonds help atoms achieve a noble gas electron configuration, typically by sharing electrons to complete their octets.
🚫 The concept of 'expanded octet' is introduced, where atoms with empty d orbitals can accommodate more than eight electrons, thus deviating from the traditional octet rule.
📚 The script clarifies that while BF3 and NH3 adhere to the octet rule, PCl5 is an example of an expanded octet, with the phosphorus atom stabilizing with more than eight electrons.
📝 The video script is educational, aiming to help students understand the basics of covalent bonding to solve chemistry problems, such as identifying expanded octets in molecules.
👨‍🏫 The instructor encourages engagement, suggesting that viewers like the video, comment with questions or suggestions, and subscribe for more educational content.

Q & A

What is the main topic discussed in the script?
-The main topic discussed in the script is covalent bonding in chemistry, focusing on the concept of electron sharing between atoms to form chemical bonds.
How does covalent bonding differ from ionic bonding?
-Covalent bonding involves the sharing of electron pairs between atoms, unlike ionic bonding which involves the transfer of electrons from one atom to another, typically between a metal and a non-metal.
What is the basis of covalent bonding?
-The basis of covalent bonding is the sharing of electron pairs to achieve stability, often by fulfilling the octet rule where atoms share electrons to complete their outer electron shell.
What is the role of the octet rule in covalent bonding?
-The octet rule plays a significant role in covalent bonding as it states that atoms tend to share, gain, or lose electrons to achieve a stable electron configuration, typically having eight electrons in their valence shell, similar to noble gases.
Can you explain the example of Cl2 given in the script?
-The script uses Cl2 as an example to illustrate covalent bonding. Each chlorine atom has seven valence electrons and shares one with the other to complete its octet, resulting in a mutual sharing of one electron pair between the two chlorine atoms.
What are the different types of covalent bonds mentioned in the script?
-The script mentions three types of covalent bonds: single bond (one shared electron pair), double bond (two shared electron pairs), and triple bond (three shared electron pairs).
How are covalent bonds represented in chemical structures?
-Covalent bonds are represented in chemical structures by lines connecting the bonded atoms. A single line represents a single bond, a double line represents a double bond, and a triple line represents a triple bond.
What are the three main ways to represent a molecule mentioned in the script?
-The script mentions three main ways to represent a molecule: molecular formula, electronic formula (also known as Lewis structure), and structural formula.
What is the significance of the term 'expanded octet' in the context of the script?
-The term 'expanded octet' refers to a situation where an atom in a molecule can accommodate more than eight electrons in its valence shell, typically by using empty d orbitals, which is an exception to the standard octet rule.
Which of the given molecules in the exercise (BF3, NH3, PCl5, BeH2, and Al3) exhibits an expanded octet?
-Among the given molecules, PCl5 exhibits an expanded octet because the phosphorus atom in PCl5 can accommodate more than eight electrons in its valence shell.
What is the difference between covalent and coordinate covalent bonding as briefly mentioned in the script?
-While the script does not deeply explore the difference, covalent bonding typically involves equal sharing of electrons, whereas coordinate covalent bonding involves the donation of a lone pair of electrons from one atom to another, which contributes to the formation of a covalent bond without providing an electron itself.

Outlines

00:00

🔬 Chemistry Lesson on Covalent Bonds

This paragraph introduces the topic of covalent bonds, contrasting them with ionic bonds. The focus is on the sharing of electron pairs, which is fundamental to covalent bonding. The script uses the example of Cl2 to illustrate how two chlorine atoms each share one electron to achieve stability, following the octet rule. The concept is simplified with an analogy to borrowing and lending video games to achieve mutual satisfaction. The paragraph also explains that covalent bonds can occur between atoms that tend to gain electrons and can be single, double, or triple bonds, depending on the number of electron pairs shared.

05:02

📚 Representations of Molecules and Covalent Bonding

This segment discusses the different ways to represent molecules, highlighting molecular formula, electronic formula, and structural formula. The molecular formula shows the types and quantities of atoms in a molecule, the electronic formula uses dots or crosses to represent valence electrons, and the structural formula illustrates the bonding structure. The paragraph concludes with an exercise from the ENEM (National High School Exam in Brazil), which asks to identify a molecule with an expanded octet. The analysis of BF3, NH3, PCl5, BeH2, and Al3 is provided, with PCl5 being the correct answer as it is the only molecule with an expanded octet, accommodating more than eight electrons in the valence shell.

10:02

📢 Engaging with the Audience and Closing Remarks

The final paragraph is a call to action for viewers to like, comment, and share the video if they found it helpful. It encourages viewers to subscribe to the channel and turn on notifications to stay updated with new content. The script also invites viewers to engage with the community by asking questions or making suggestions. The closing is warm and inviting, thanking the audience and signaling the end of the lesson on covalent bonding.

Mindmap

Keywords

💡Covalent Bonds

Covalent bonds are a type of chemical bond where atoms share one or more pairs of electrons. In the video, the concept is central to understanding how atoms achieve stability by sharing electrons to fill their outer electron shells, as illustrated by the example of Cl2 molecules where two chlorine atoms share electrons to complete their octets.

💡Electron Sharing

Electron sharing is the process by which two atoms share one or more electrons to satisfy the octet rule. The video script explains that unlike ionic bonds where electrons are transferred, covalent bonds involve a mutual sharing of electrons, as in the case of hydrogen molecules (H2) where one electron is shared between two hydrogen atoms.

💡Octet Rule

The octet rule states that atoms are most stable when they have eight electrons in their outermost shell. The video emphasizes this rule in the context of covalent bonding, where atoms share electrons to achieve this stable configuration, which is a key principle in understanding the formation of molecules like Cl2.

💡Ionic Bonds

Ionic bonds are mentioned in contrast to covalent bonds. They occur between a metal and a non-metal, where one atom transfers electrons to another, resulting in the formation of ions. The video script explains that ionic bonds differ from covalent bonds in that they involve electron transfer rather than sharing.

💡Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom, which are involved in chemical bonding. The video discusses how atoms with seven valence electrons, like chlorine, will share one electron to achieve a stable configuration, highlighting the role of valence electrons in covalent bonding.

💡Molecular Formula

A molecular formula represents the exact number of atoms of each element within a molecule. The video uses the example of I2 to explain how the molecular formula indicates the composition of a molecule, showing that it consists of two iodine atoms.

💡Electron Dot Structure

Electron dot structures, also known as Lewis structures, are diagrams that represent the valence electrons of atoms in a molecule. The video script mentions these structures as a way to visualize the sharing of electrons in covalent bonds, such as in the case of oxygen gas (O2) where two pairs of electrons are shared.

💡Single, Double, and Triple Bonds

These terms refer to the number of electron pairs shared between atoms in a covalent bond. The video explains that a single bond involves one pair of shared electrons, a double bond involves two pairs, and a triple bond involves three pairs, using the example of nitrogen gas (N2) to illustrate a triple bond.

💡Expanded Octet

An expanded octet occurs when an atom has more than eight electrons in its valence shell. The video discusses this concept in the context of molecules like PCl5, where the central phosphorus atom accommodates more than eight electrons, thus expanding its octet to achieve stability.

💡Chemical Stability

Chemical stability refers to the resistance of a substance to undergo a chemical reaction. The video script connects the concept of covalent bonding to achieving stability, as atoms form bonds to complete their octets and reach a stable electron configuration, which is a fundamental aspect of chemical bonding.

Highlights

Introduction to covalent bonds, contrasting with ionic bonds, emphasizing electron sharing rather than transfer.

Explanation of covalent bond formation using the example of Cl2 molecule, adhering to the octet rule.

Simplification of electron sharing in covalent bonds through the analogy of lending video games.

Discussion on the occurrence of covalent bonds between hydrogen, non-metals, and metals to achieve stability.

Different types of covalent bonds: single, double, and triple bonds, based on the number of electron pairs shared.

Representation of covalent bonds with single, double, and triple lines in chemical structures.

Explanation of molecular formulas, electronic formulas, and structural formulas to represent molecules.

Practical exercise to identify molecules with expanded octets, focusing on atoms with more than eight valence electrons.

Analysis of BF3, NH3, PCl5, BeH2, and Al3 molecules to determine which one has an expanded octet.

Identification of PCl5 as the molecule with an expanded octet, accommodating more than eight electrons in the valence shell.

Clarification on the difference between covalent bonds and coordinate covalent bonds, and their exceptions to the octet rule.

Encouragement for students to review the concept of covalent bonds and their exceptions for better understanding and exam preparation.

Invitation for students to like, comment, and share the video for further engagement and support.

Reminder to subscribe to the channel and turn on notifications for updates on new content.

Closing remarks, thanking the audience and signaling the end of the lesson on covalent bonds.