Problem 42 - Chemistry The Central Science In Si Units

Question

Arrange the bonds in each of the following sets in order of increasing polarity: \((\mathbf{a}) \mathrm{C}-\mathrm{F}, \mathrm{O}-\mathrm{F}, \mathrm{Be}-\mathrm{F} ;\) (b) \(\mathrm{O}-\mathrm{Cl}, \mathrm{S}-\mathrm{Br}, \mathrm{C}-\mathrm{P} ;(\mathbf{c}) \mathrm{C}-\mathrm{S}, \mathrm{B}-\mathrm{F}, \mathrm{N}-\mathrm{O}\).

Step-by-Step Solution

Answer

(a) O-F, C-F, Be-F; (b) S-Br, C-P, O-Cl; (c) C-S, N-O, B-F.

Step 1: Understand Bond Polarity

Bond polarity depends on the difference in electronegativity between the two atoms involved in a bond. The greater the difference, the more polar the bond is. To solve the problem, we need to know the electronegativity values for each atom involved.

Step 2: Electronegativity Values

Find the electronegativity values for the relevant elements: - Fluorine (F) = 4.0 - Oxygen (O) = 3.5 - Carbon (C) = 2.5 - Beryllium (Be) = 1.5 - Chlorine (Cl) = 3.0 - Sulfur (S) = 2.5 - Bromine (Br) = 2.8 - Phosphorous (P) = 2.1 - Nitrogen (N) = 3.0

Step 3: Calculate Electronegativity Differences

For each bond, calculate the difference in electronegativity: (a) - C-F: |2.5 - 4.0| = 1.5 - O-F: |3.5 - 4.0| = 0.5 - Be-F: |1.5 - 4.0| = 2.5 (b) - O-Cl: |3.5 - 3.0| = 0.5 - S-Br: |2.5 - 2.8| = 0.3 - C-P: |2.5 - 2.1| = 0.4 (c) - C-S: |2.5 - 2.5| = 0.0 - B-F: |2.0 - 4.0| = 2.0 - N-O: |3.0 - 3.5| = 0.5

Step 4: Order Bonds by Increasing Polarity

Arrange the bonds by their electronegativity difference from lowest to highest: (a) O-F (0.5), C-F (1.5), Be-F (2.5) (b) S-Br (0.3), C-P (0.4), O-Cl (0.5) (c) C-S (0.0), N-O (0.5), B-F (2.0)

Key Concepts

Electronegativity

Electronegativity is a key concept in understanding bond polarity. It is the tendency of an atom to attract electrons towards itself when forming a chemical bond. Different elements have varying degrees of electronegativity, which influences the type of bond they form.

• Fluorine is the most electronegative element with a value of 4.0, making it particularly effective at pulling electrons.
• Oxygen, with a value of 3.5, is also highly electronegative.
• Elements like Be (Beryllium, 1.5) and P (Phosphorus, 2.1) have lower electronegativities.

The difference in electronegativity values between two atoms determines the bond's polarity. A larger difference means a more polar bond, while a smaller difference means the bond is less polar or even nonpolar. Understanding electronegativity is crucial to predicting how atoms will interact and the type of bond they will form.

Covalent Bonds

Covalent bonds form when atoms share electrons, allowing them to fill their outer electron shells and achieve stability. Unlike ionic bonds, which result from the transfer of electrons, covalent bonds involve a sharing mechanism.

• Homogeneous covalent bonds, such as \( \text{O}_2 \), involve atoms with similar electronegativities, leading to equal sharing of electrons.
• Heterogeneous covalent bonds, like \( \text{H}_2\text{O} \), involve atoms with different electronegativities, causing unequal sharing.

This degree of electron sharing determines the bond type: whether it is purely covalent (equal sharing), polar covalent (unequal sharing due to a moderate difference in electronegativity), or ionic (significant difference leading to electron transfer). Covalent bonds are typically found in organic compounds and molecules with non-metal elements.

Chemical Bonding

Chemical bonding is the force that holds atoms together in compounds. Understanding the types of bonds - ionic, covalent, and metallic - is essential for grasping how substances are formed.

• Ionic bonds occur when electrons are transferred from one atom to another, often between metals and non-metals, leading to full positive and negative charges.
• In contrast, covalent bonds involve the sharing of electrons between non-metal atoms.
• Metallic bonds, however, involve a pooling of electrons among metal atoms, contributing to properties like conductivity and malleability.

Different bonds dictate the properties and behaviors of substances. Covalent bonds create molecules with definite structures, whereas ionic compounds form crystal lattices. The type of bonding also influences a compound's chemical and physical properties like melting point, hardness, and electrical conductivity. Understanding chemical bonding is fundamental to chemistry and underlies the behavior of materials in our daily lives.