Question

In each case, which of the following pairs of bonded elements forms the more polar bond? a. \(\mathrm{Br}-\mathrm{Cl}\) or \(\mathrm{Br}-\mathrm{F}\) b. As \(-\mathrm{S}\) or \(\mathrm{As}-\mathrm{O}\) c. \(\mathrm{Pb}-\mathrm{C}\) or \(\mathrm{Pb}-\mathrm{Si}\)

Short answer

a. \(\mathrm{Br}-\mathrm{F}\) is more polar b. \(\mathrm{As}-\mathrm{O}\) is more polar c. \(\mathrm{Pb}-\mathrm{Si}\) is more polar

Step-by-step solution

Identifying the electronegativities of the elements

To determine the polarity of the given bonds, we first need to know the electronegativities of the elements involved. Refer to an electronegativity table or use the periodic table to find these values: - Bromine (Br): 2.96 - Chlorine (Cl): 3.16 - Fluorine (F): 3.98 - Arsenic (As): 2.18 - Sulfur (S): 2.58 - Oxygen (O): 3.44 - Lead (Pb): 2.33 - Carbon (C): 2.55 - Silicon (Si): 1.90

Calculate electronegativity differences for each bond

Now, we need to calculate the electronegativity differences for each of the given bonds in the exercise. Subtract the smaller value from the larger one for each pair: a. \(|2.96 - 3.16|\) for Br-Cl and \(|2.96 - 3.98|\) for Br-F b. \(|2.18 - 2.58|\) for As-S and \(|2.18 - 3.44|\) for As-O c. \(|2.33 - 2.55|\) for Pb-C and \(|2.33 - 1.90|\) for Pb-Si

Compare the electronegativity differences

Compare the electronegativity differences to determine which bond is more polar within each pair: a. Br-Cl: \(|2.96 - 3.16|\) = 0.20; Br-F: \(|2.96 - 3.98|\) = 1.02 b. As-S: \(|2.18 - 2.58|\) = 0.40; As-O: \(|2.18 - 3.44|\) = 1.26 c. Pb-C: \(|2.33 - 2.55|\) = 0.22; Pb-Si: \(|2.33 - 1.90|\) = 0.43

Identify the more polar bond within each pair

The bond with the larger electronegativity difference is more polar. Thus, for each pair, we have: a. Br-F is more polar than Br-Cl because 1.02 > 0.20 b. As-O is more polar than As-S because 1.26 > 0.40 c. Pb-Si is more polar than Pb-C because 0.43 > 0.22 In conclusion: a. \(\mathrm{Br}-\mathrm{F}\) is more polar b. \(\mathrm{As}-\mathrm{O}\) is more polar c. \(\mathrm{Pb}-\mathrm{Si}\) is more polar

Key concepts

Understanding Electronegativity

Electronegativity is a key concept in chemistry education essential for understanding molecular interactions. It refers to an atom's ability to attract and hold electrons when forming a chemical bond. Some atoms are more "greedy" for electrons than others, and this greediness is what we measure as electronegativity. Electronegativity values are usually available in charts or the periodic table, with higher numbers indicating stronger attractions for electrons.

• Bromine (Br) has an electronegativity of 2.96, while Fluorine (F) has the highest at 3.98.
• Comparatively, Lead (Pb) is much less electronegative at 2.33.

Understanding how these values relate to each other helps predict chemical behaviors. For example, when determining which bond in a molecule is more polar, we compare the electronegativities of the bonded atoms. The atom with higher electronegativity will pull the shared electrons closer to itself, creating a polarized bond.

Exploring Bond Polarity

Bond polarity occurs when electrons in a bond are not shared equally between two atoms. This inequality arises because one atom attracts the electrons more than the other, based on their differences in electronegativity. A polar bond has a partial positive charge on one end and a partial negative charge on the other, akin to a magnet.

• In the bond between bromine (Br) and fluorine (F), fluorine attracts the electrons more strongly, making Br-F a polar bond.
• Conversely, a bond between similar elements or those with equal electronegativities would be nonpolar.

The larger the difference in electronegativity between two bonded atoms, the more significant the charge separation, and the more polar the bond is. Thus, calculating these differences helps in predicting the molecule's structure and reactivity.

Chemistry Education and Polar Bonds

Understanding polar bonds is vital in chemistry education as it lays the foundation for grasping more complex chemical behavior. Knowing how to calculate electronegativity differences allows students to predict polarity and therefore anticipate molecular geometry, the behavior of molecules in a magnetic field, and solubility trends.

• Polar bonds are critical in biochemical processes, influencing how molecules like proteins and DNA interact.
• They determine important properties like a molecule's boiling point and solubility, which are essential in chemical reactions and product development.

Teaching students to apply these concepts in practical situations helps them develop a deeper appreciation for the nuances in chemical reactions and the compounds that facilitate everyday life. This knowledge not only advances their scientific literacy but also equips them with tools to understand the molecular world.