Question

For each pair, indicate the more polar bond by circling the negative end of its dipole. a. \(C-S, C-O\) b. \(C-F, C-N\) c. \(P-H, P-C l\)

Short answer

For each pair, the more polar bond and the negative end of its dipole are: a. C-O bond, with the negative end on the Oxygen atom. b. C-F bond, with the negative end on the Fluorine atom. c. P-Cl bond, with the negative end on the Chlorine atom.

Step-by-step solution

Recall electronegativity values

Electronegativity is a measure of how strongly an atom attracts the electrons in a bond. We'll need to know the approximate electronegativity values of the involved atoms: - Carbon (C): 2.5 - Sulfur (S): 2.58 - Oxygen (O): 3.44 - Fluorine (F): 3.98 - Nitrogen (N): 3.04 - Phosphorus (P): 2.19 - Hydrogen (H): 2.20 - Chlorine (Cl): 3.16

Compare electronegativity values for pair (a)

For the C-S bond and the C-O bond, we will compare electronegativity values of Carbon with Sulfur, and Carbon with Oxygen. - C-S bond: C (2.5) and S (2.58) - C-O bond: C (2.5) and O (3.44) Since Oxygen has a higher electronegativity value, the C-O bond is more polar, with the negative end on the Oxygen atom.

Compare electronegativity values for pair (b)

Let's compare the electronegativity values for C-F and C-N bonds. - C-F bond: C (2.5) and F (3.98) - C-N bond: C (2.5) and N (3.04) Here, Fluorine has a higher electronegativity value. Thus, the C-F bond is more polar, with the negative end on the Fluorine atom.

Compare electronegativity values for pair (c)

Now, let's compare the electronegativity values for P-H and P-Cl bonds. - P-H bond: P (2.19) and H (2.20) - P-Cl bond: P (2.19) and Cl (3.16) Chlorine has a higher electronegativity value. Therefore, the P-Cl bond is more polar, with the negative end on the Chlorine atom.

Key concepts

Electronegativity

Electronegativity is a pivotal concept in chemistry that explains a lot about how atoms interact with each other. At its essence, electronegativity is a measure of an atom's ability to attract and hold onto electrons when forming chemical bonds.

The trend in the periodic table shows that electronegativity increases as you move from left to right across a period and decreases as you go down a group. For example, fluorine is the most electronegative element because it's at the top right corner of the periodic table (excluding the noble gases).

Why does this matter? In a bond, if one atom has higher electronegativity than another, it will more strongly attract the electrons in the bond, making the bond polar. This difference in electronegativity can be used to predict which molecule will have a more polar bond, like in the exercise where we compared different pairs of atoms.

Chemical Bonding

Chemical bonding is the force that holds atoms together in molecules. There are different types of chemical bonds: ionic, covalent, and metallic. Covalent bonds, in particular, are where we commonly find polar and nonpolar bonds.

In a covalent bond, atoms share electrons, but they don't always share them equally. When the atoms involved in the bond possess the same or similar electronegativity, the electrons can be shared equally, leading to a nonpolar covalent bond. However, when there is a significant difference in electronegativity between the atoms, one atom attracts the electrons more strongly, resulting in a polar covalent bond.

Understanding the type of bond and the respective electronegativities of the atoms involved is key to understanding the properties of the molecule, such as solubility, boiling point, and electrical conductivity.

Dipole Moments

A dipole moment is a mathematical quantity that measures the separation of positive and negative charges in a molecule. It's a vector, which means it has both magnitude and direction.

The larger the difference in electronegativity between the atoms in a bond, the greater the dipole moment. A polar bond has a dipole moment where the direction points from the positive end (less electronegative atom) to the negative end (more electronegative atom). This is why in the exercise, we circled the negative end of the dipole to indicate the direction of the bond's polarity.

Dipole moments are incredibly useful because they give us insight into the molecule's overall polarity and how it might interact with other molecules. They contribute to physical properties such as boiling point and solubility and can help predict the bond's behavior in electric fields.