Question

Classify each bond as nonpolar covalent or polar covalent or state that ions are formed. (a) \(\mathrm{S}-\mathrm{H}\) (b) \(\mathrm{P}-\mathrm{H}\) (c) \(\mathrm{C}-\mathrm{F}\) (d) \(\mathrm{C}-\mathrm{Cl}\)

Short answer

Question: Classify the following bonds as nonpolar covalent, polar covalent, or ionic: (a) S-H, (b) P-H, (c) C-F, and (d) C-Cl. Answer: (a) S-H is a nonpolar covalent bond. (b) P-H is a nonpolar covalent bond. (c) C-F is a polar covalent bond. (d) C-Cl is a polar covalent bond.

Step-by-step solution

(a) Determine electronegativity difference for S-H bond

The electronegativity value for sulfur (S) is 2.58, and for hydrogen (H) it is 2.20. Thus, the electronegativity difference between the two in the S-H bond is: \(|2.58 - 2.20| = 0.38\).

(a) Classify the S-H bond

Since the electronegativity difference is 0.38, which is less than 0.5, the S-H bond is considered a nonpolar covalent bond.

(b) Determine electronegativity difference for P-H bond

The electronegativity value for phosphorus (P) is 2.19, and for hydrogen (H) it is 2.20. Thus, the electronegativity difference between the two in the P-H bond is: \(|2.19 - 2.20| = 0.01\).

(b) Classify the P-H bond

Since the electronegativity difference is 0.01, which is less than 0.5, the P-H bond is considered a nonpolar covalent bond.

(c) Determine electronegativity difference for C-F bond

The electronegativity value for carbon (C) is 2.55, and for fluorine (F) it is 3.98. Thus, the electronegativity difference between the two in the C-F bond is: \(|2.55 - 3.98| = 1.43\).

(c) Classify the C-F bond

Since the electronegativity difference is 1.43, which is between 0.5 and 2.0, the C-F bond is considered a polar covalent bond.

(d) Determine electronegativity difference for C-Cl bond

The electronegativity value for carbon (C) is 2.55, and for chlorine (Cl) it is 3.16. Thus, the electronegativity difference between the two in the C-Cl bond is: \(|2.55 - 3.16| = 0.61\).

(d) Classify the C-Cl bond

Since the electronegativity difference is 0.61, which is between 0.5 and 2.0, the C-Cl bond is considered a polar covalent bond.

Key concepts

Nonpolar Covalent Bonds

Nonpolar covalent bonds occur when electrons are shared equally between two atoms. In these bonds, the difference in electronegativity between the atoms is less than 0.5.
This minimal difference means that neither atom has a strong pull on the shared electrons. As a result, the electron cloud remains balanced around both nuclei.

• For a bond like S-H, with an electronegativity difference of 0.38, the bond is classified as nonpolar covalent.
• Similarly, the P-H bond has an electronegativity difference of 0.01, confirming it as nonpolar covalent.

This equal sharing is often found in diatomic molecules consisting of the same element, such as O₂. It's a simple yet essential concept in understanding molecular behavior and stability.

Polar Covalent Bonds

Polar covalent bonds form when electrons are shared unequally between atoms. This usually occurs when the electronegativity difference is between 0.5 and 2.0.
The atom with higher electronegativity attracts the shared electrons more, creating a partial negative charge. The less electronegative atom takes on a partial positive charge.

• In a C-F bond, the electronegativity difference is 1.43, making it polar covalent, with fluorine pulling the shared electrons closer.
• The C-Cl bond has a difference of 0.61, causing chlorine to slightly dominate the shared electrons, resulting in a polar bond.

This unequal sharing leads to dipole moments, where the molecule has a slight electrical polarity. Understanding these bonds helps in predicting a molecule's physical properties, such as solubility and boiling point.

Ionic Bonds

Ionic bonds arise when one atom completely transfers one or more electrons to another, creating ions. These bonds usually form when the electronegativity difference is greater than 2.0.
One atom becomes a positively charged cation, while the other becomes a negatively charged anion. The strong electrostatic attraction between these opposite charges holds the compound together.

• Common in compounds like NaCl, where sodium donates an electron to chlorine.
• These bonds result in crystalline structures with distinct physical properties like high melting points.

Ionic bonds are key in forming many salts and minerals. Unlike covalent bonds, they do not share electrons but rather transfer them, resulting in a distinctly different type of chemical interaction.