Question

The most polar covalent species among the ones listed is: (a) \(\mathrm{C}-\mathrm{S}\) (b) \(\mathrm{C}-\mathrm{O}\) (c) \(\mathrm{C}-\mathrm{F}\) (d) \(\mathrm{C}-\mathrm{Br}\)

Short answer

The most polar covalent species is \(\mathrm{C}-\mathrm{F}\).

Step-by-step solution

Understand Polarity

Polarity in covalent bonds arises from differences in electronegativity between the bonded atoms. The greater the difference in electronegativity, the more polar the bond.

Determine Electronegativity Values

The electronegativity values for the elements involved are: Carbon (C) = 2.55, Sulfur (S) = 2.58, Oxygen (O) = 3.44, Fluorine (F) = 3.98, Bromine (Br) = 2.96. Use these values to find the differences that determine bond polarity.

Calculate Electronegativity Differences

Calculate the electronegativity differences for each bond: - C-S: |2.55 - 2.58| = 0.03 - C-O: |2.55 - 3.44| = 0.89 - C-F: |2.55 - 3.98| = 1.43 - C-Br: |2.55 - 2.96| = 0.41

Identify the Most Polar Bond

The most polar bond has the greatest difference in electronegativity. From the calculated differences: - C-F has the highest difference of 1.43, making it the most polar bond.

Key concepts

Electronegativity

Electronegativity is a measure of an atom's ability to attract shared electrons in a chemical bond. When atoms form a bond, the electron pairs are not always shared equally. Electronegativity determines how strongly an atom attracts electrons towards itself.
The higher the electronegativity of an atom, the stronger its pull on electrons. This is an inherent property of each element. For instance, in the exercise, Fluorine (F) has the highest electronegativity with a value of 3.98, indicating a very strong ability to attract electrons.

• Higher Electronegativity: Stronger pull on electrons
• More significant differences in electronegativity lead to polar bonds
• Electronegativity values can predict bond behavior

Understanding these values is crucial for determining bond characteristics during problem-solving in chemistry.

Bond Polarity

Bond polarity arises due to the difference in electronegativity between two bonded atoms. When two atoms with different electronegativity values form a covalent bond, the shared electrons are pulled more toward the atom with the higher electronegativity.
This causes one end of the molecule to be slightly negative and the other slightly positive, creating a polar covalent bond.
In the exercise example, the

• C-F bond is the most polar due to the greatest difference in electronegativity, creating strong dipoles.
• C-S bond, with nearly the same electronegativity, is the least polar, exhibiting a nearly equal sharing of electrons.

The presence of bond polarity affects how molecules interact with each other and can influence physical properties like boiling and melting points.

Covalent Bonding

Covalent bonding involves the sharing of electrons between two atoms. This type of bond is commonly seen in molecular compounds where nonmetals bond together.
Covalent bonds can be either nonpolar or polar depending on the electronegativity difference.

• Nonpolar Covalent Bonds: Electrons are shared equally. Usually occurs between atoms of the same element or those with similar electronegativity (e.g., C-H bond).
• Polar Covalent Bonds: Unequal sharing of electrons due to significant differences in electronegativity (e.g., C-F bond is polar).

Understanding whether a bond is covalent and its polarity is essential for predicting molecular behavior, reactivity, and physical properties within chemistry problem-solving.

Chemistry Problem-Solving

Approaching problems in chemistry like determining bond polarity can be systematic. Let's break it down into manageable steps: 1. **Identify the Elements Involved**: List the atoms participating in the bond. 2. **Determine Electronegativity Values**: Use a reference table for electronegativity values. 3. **Calculate Differences**: Subtract the smaller electronegativity from the larger one. 4. **Analyze Bond Types**: - Large differences suggest polar covalent bonds. - Small or zero differences suggest nonpolar covalent bonds. By following these steps, as demonstrated in the exercise, students can easily solve problems related to bond polarity. This systematic approach also helps in understanding underlying chemical concepts, making complex topics more accessible. Mastery in chemistry problem-solving comes with practice and familiarity with these methods.