Question

Without using Fig. \(3-4,\) predict which bond in each of the following groups will be the most polar. a. \(\mathrm{C}-\mathrm{H}, \mathrm{Si}-\mathrm{H}, \mathrm{Sn}-\mathrm{H}\) \(\mathbf{b .}\) Al- \(\mathbf{B r}, \mathbf{G a}-\mathbf{B r}, \operatorname{In}-\mathbf{B r}, \mathbf{T}-\mathbf{B r}\) c. \(C-O\) or \(S i-O\) d. \(\mathrm{O}-\mathrm{F}\) or \(\mathrm{O}-\mathrm{Cl}\)

Short answer

The most polar bonds for each group are: a. C-H b. Al-Br c. Si-O d. O-F and O-Cl (equally polar)

Step-by-step solution

Identify given bonds and atoms

In this exercise we have four groups of bonds: a. C-H, Si-H, Sn-H b. Al-Br, Ga-Br, In-Br, T-Br (where T = Thallium) c. C-O, Si-O d. O-F, O-Cl

Recall electronegativity values of the involved atoms

To determine the most polar bond, we need to calculate and compare the electronegativity differences between the bonded atoms for each group. The approximate electronegativity values for the elements are: C: 2.5, H: 2.1, Si: 1.8, Sn: 1.8, Al: 1.5, Br: 2.8, Ga: 1.6, In: 1.7, T: 1.8, O: 3.5, F: 4.0, Cl: 3.0

Calculate the electronegativity differences

Using the electronegativity values, we can calculate the differences for each bond in each group: a. |2.5 - 2.1| = 0.4 (C-H), |1.8 - 2.1| = 0.3 (Si-H), |1.8 - 2.1| = 0.3 (Sn-H) b. |1.5 - 2.8| = 1.3 (Al-Br), |1.6 - 2.8| = 1.2 (Ga-Br), |1.7 - 2.8| = 1.1 (In-Br), |1.8 - 2.8| = 1 (T-Br) c. |2.5 - 3.5| = 1 (C-O), |1.8 - 3.5| = 1.7 (Si-O) d. |3.5 - 4.0| = 0.5 (O-F), |3.5 - 3.0| = 0.5 (O-Cl)

Identify the most polar bond in each group

From the electronegativity differences calculated, we can identify the most polar bond in each group: a. Most polar bond: C-H (0.4) b. Most polar bond: Al-Br (1.3) c. Most polar bond: Si-O (1.7) d. Equally polar bonds: O-F (0.5) and O-Cl (0.5) So, the most polar bonds for each group are C-H, Al-Br, Si-O, and both O-F and O-Cl (equally polar).

Key concepts

Electronegativity

Electronegativity is a fundamental concept in chemistry that refers to the tendency of an atom to attract electrons to itself when it is part of a compound. Developed by Linus Pauling, this property is a numerical value that can help us predict many properties of molecules, including the types and strengths of bonds they may form.

For instance, elements with high electronegativity, such as fluorine (which has the highest electronegativity of 4.0), are very effective at attracting electrons towards themselves. This contrast with elements like cesium and francium, which have very low electronegativities and thus a lower propensity for attracting electrons.

In the context of the textbook exercise, by considering the electronegativity values of the involved atoms, we can predict which bonds will be the most polar. The greater the difference in electronegativity between two bonded atoms, the more polar the bond. Therefore, by consulting a periodic table or reference materials for electronegativity values, it becomes a straightforward exercise to determine bond polarity - by subtracting the electronegativity values of the bonded atoms and analyzing the resultant difference.

Polar Bond

Chemical bonds, specifically polar bonds, play a crucial role in the structure and properties of molecules. A polar bond is a type of covalent bond where the electrons forming the bond are unequally distributed. This occurs because of the different electronegativities of the atoms involved, leading to a partial positive charge on one atom and a partial negative charge on the other.

The polarity of a bond has significant implications for the physical properties of the substance, such as its boiling point, melting point, and solubility in various solvents. For example, water is a polar molecule, which is why it's such an effective solvent for a range of substances. In the exercises, by calculating the electronegativity differences, we identified which bonds are most polar: C-H, Al-Br, Si-O, and to a similar extent, O-F and O-Cl.

Understanding the concept of polar bonds allows us not only to predict molecular behavior but also to grasp the interactions between different substances in complex chemical reactions.

Chemical Bonding

Chemical bonding is the force that holds atoms together in molecules, determining the structure and stability of the molecule. There are three main types of chemical bonds: ionic, covalent, and metallic. Ionic bonds form between metals and nonmetals and involve the transfer of electrons. Covalent bonds, like the ones discussed in the textbook exercise, involve the sharing of electrons between nonmetals. Metallic bonds are the forces holding metals together, involving a 'sea' of delocalized electrons shared among a lattice of metal atoms.

Each type of bonding has unique properties and is critical for predicting the behavior of substances. The type and strength of bonds affect the chemical and physical properties of molecules, influencing how they interact with their environment.

In our exercises, we focused on covalent bonds, specifically looking at how the differences in electronegativity lead to bond polarity, which in turn dictates the interactions each molecule can have. For example, in group a of the exercise, when comparing C-H, Si-H, and Sn-H, it was crucial to understand that carbon with a higher electronegativity than silicon or tin forms a more polar covalent bond with hydrogen.