Unit 4 Chemical Bonds Concept 4 Notes

Summary

This lesson dives into covalent bonds, explaining how atoms share electrons to form molecules. Covalent compounds, formed between non-metals, can be polar or nonpolar based on electronegativity differences. The video introduces naming conventions, emphasizing the use of prefixes (like di-, tri-) and the suffix '-ide' for the second element. The script also covers writing chemical formulas from names, where prefixes indicate the number of atoms. Finally, the concept of VSEPR Theory is briefly touched upon, which helps determine the 3D shapes of molecules. Practical examples and exercises are included to reinforce learning.

Takeaways

• 😀 Covalent bonds form when two or more non-metal atoms share electrons to create molecules.
• 😀 The difference in electronegativity (ΔEN) between atoms determines whether a bond is polar or nonpolar covalent.
• 😀 Polar covalent bonds occur when there is a difference in electronegativity, leading to unequal electron sharing.
• 😀 Nonpolar covalent bonds occur when two atoms have identical electronegativity, resulting in equal sharing of electrons.
• 😀 A molecule is a neutral group of atoms bonded by covalent bonds, whereas ionic compounds form crystal structures with charged ions.
• 😀 Diatomic elements (e.g., H2, N2, O2) naturally exist as molecules with nonpolar covalent bonds between identical atoms.
• 😀 Covalent compounds typically follow the octet rule, aiming to achieve a full outer electron shell.
• 😀 Covalent bonds can be single, double, or triple, depending on how many pairs of electrons are shared between atoms.
• 😀 VSEPR theory (Valence Shell Electron Pair Repulsion) helps predict the 3D shapes of molecules by considering electron pair repulsion.
• 😀 Naming covalent compounds involves using prefixes to indicate the number of atoms and adding an '-ide' suffix to the second element.
• 😀 When converting from a compound's name to its chemical formula, prefixes in the name indicate the subscripts in the formula (e.g., 'di' means 2, 'mono' means 1).

Q & A

What is the main difference between covalent bonds and ionic bonds?

Covalent bonds involve the sharing of electrons between non-metal atoms, while ionic bonds involve the transfer of electrons between a metal and a non-metal, forming charged ions.

How can we classify a covalent bond as polar or nonpolar?

A covalent bond is polar if there is a difference in electronegativity (Delta EN) between the two atoms, causing unequal sharing of electrons. If there is no difference in electronegativity, the bond is nonpolar, with equal sharing of electrons.

What does the term 'molecule' mean in the context of covalent compounds?

A molecule is a neutral group of atoms held together by covalent bonds. It is a single unit that exists on its own, unlike ionic compounds, which form crystal structures.

What are diatomic elements, and how do they form bonds?

Diatomic elements are molecules consisting of two atoms of the same element, such as H2, O2, N2. These elements naturally form nonpolar covalent bonds, as the atoms equally share electrons.

What is the significance of the octet rule in covalent bonding?

The octet rule states that atoms tend to share electrons in a way that gives them a full outer electron shell, typically with eight electrons, which is considered a stable configuration.

How do single, double, and triple covalent bonds differ?

In a single covalent bond, two electrons are shared. A double bond involves four shared electrons, while a triple bond involves six shared electrons, making the bond stronger as the number of shared electrons increases.

What is the VSEPR theory and how does it relate to the shape of molecules?

The VSEPR (Valence Shell Electron Pair Repulsion) theory states that electron pairs around a central atom will arrange themselves as far apart as possible to minimize repulsion. This theory helps predict the three-dimensional shape of molecules.

How do you name a covalent compound based on its chemical formula?

To name a covalent compound, first name the first element without a prefix unless there is more than one atom. Then name the second element with a prefix to indicate the number of atoms, and add an 'ide' suffix.

What are the prefixes used in naming covalent compounds, and what do they represent?

The prefixes used in naming covalent compounds are: mono (1), di (2), tri (3), tetra (4), penta (5), and so on. They indicate the number of atoms of each element in the compound.

What does the absence of a prefix for the first element in a compound indicate?

The absence of a prefix for the first element indicates that there is only one atom of that element in the compound. For example, 'carbon' in CO2 indicates a single carbon atom.