AP Chemistry · Learn by Concept

AP Chemistry Help: Types Of Chemical Bonds

Review real example questions for Types Of Chemical Bonds in AP Chemistry.

Question 1 / 10

0 of 10 answered

Which of the following molecules contains both polar covalent bonds and nonpolar covalent bonds?

All questions

Question 1

Which of the following molecules contains both polar covalent bonds and nonpolar covalent bonds?

$H_2O$
$C_2H_4$
$H_2O_2$ (correct answer)
$CH_2Cl_2$

Explanation: To have both polar and nonpolar covalent bonds, a molecule must contain bonds between different atoms with a significant electronegativity difference (polar) and bonds between identical atoms (nonpolar). Hydrogen peroxide ( $H_2O_2$ ) has the structure H-O-O-H. The O-H bonds are polar covalent due to the electronegativity difference between oxygen and hydrogen. The O-O bond is nonpolar covalent because the two oxygen atoms have identical electronegativity.

Question 2

In aluminum metal, Al atoms are bonded through delocalized valence electrons that move throughout the solid. What type of bonding best describes solid aluminum?

Polar covalent
Metallic (correct answer)
Nonpolar covalent
Ionic
London dispersion

Explanation: This question tests the ability to identify the type of chemical bond in elemental metals. In solid aluminum, Al atoms are bonded via delocalized valence electrons in a metallic structure, allowing properties like ductility. This 'electron sea' model defines metallic bonding among metal atoms. Metallic bonds are distinct from covalent or ionic. A tempting distractor is ionic, but it is incorrect without anions, misconceptions arise from lattice similarities to ionic solids. Recognize metallic bonds in pure metals by their conductivity and electron delocalization.

Question 3

Which of the following properties of aluminum is primarily explained by the delocalized nature of its valence electrons?

Its low density compared to other metals such as lead or gold.
Its ability to be drawn into wires without breaking, which is known as ductility. (correct answer)
Its chemical reactivity, such as the formation of a protective oxide layer on its surface.
Its existence as a solid with a specific crystal structure at room temperature.

Explanation: The delocalized 'sea of electrons' model of metallic bonding explains properties like electrical conductivity, malleability, and ductility. Ductility is the ability to be drawn into a wire. This is possible because the metal cations can slide past one another within the electron sea without disrupting the overall metallic bonding. The delocalized electrons continue to hold the repositioned cations together. Density is related to atomic mass and packing, while chemical reactivity relates to electron configuration and ionization energy.

Question 4

The bonds in a certain compound have significant ionic character but are best classified as polar covalent. Which of the following pairs of atoms is most likely to form such a bond?

Na and F
Al and Cl (correct answer)
Cl and F
C and S

Explanation: The character of a bond exists on a continuum. While bonds between metals and nonmetals are often considered ionic, the electronegativity difference provides a more nuanced view. The electronegativity difference between Al (EN ≈ 1.6) and Cl (EN ≈ 3.2) is approximately 1.6. This value falls in the range typically classified as polar covalent, but it is large enough to imply significant ionic character. In contrast, Na-F has a very large electronegativity difference and is clearly ionic. Cl-F is polar covalent, and C-S is nearly nonpolar covalent.

Question 5

In $\mathrm{CH_4(g)}$ , the electronegativity of C is 2.5 and that of H is 2.1, so $\Delta EN = 0.4$ . Which classification best describes a C–H bond in methane?

Nonpolar covalent bond (correct answer)
Polar covalent bond
Ionic bond
Metallic bond
Hydrogen bond

Explanation: This question tests the skill of classifying bonds based on electronegativity differences. The electronegativity difference between C and H is 0.4, which is at the boundary between nonpolar and polar covalent bonds, but is typically classified as nonpolar covalent. In CH₄, the small electronegativity difference means electrons are shared nearly equally between carbon and hydrogen atoms, resulting in minimal polarity in each C-H bond. Students might incorrectly choose polar covalent bond (B) by strictly applying the ΔEN = 0.4 cutoff, but C-H bonds are conventionally treated as nonpolar due to their minimal dipole moment. When ΔEN is exactly 0.4 or very close to it, especially for C-H bonds, classify as nonpolar covalent.

Question 6

In carbon dioxide, the C–O electronegativity difference is about $1.0$ (C $\approx 2.5$ , O $\approx 3.5$ ), meaning each C–O bond shares electrons unequally. What type of bond best describes a C–O bond in $\text{CO}_2$ ?

Metallic
Hydrogen bonding
Polar covalent (correct answer)
Nonpolar covalent
Ionic

Explanation: This question tests the ability to identify the type of chemical bond based on electronegativity in linear molecules. In CO₂, each C-O bond has ΔEN ≈ 1.0, leading to unequal electron sharing and polar covalent character. The oxygen atoms pull electrons more, creating partial charges, though the molecule is nonpolar overall due to symmetry. Polar covalent bonds are defined by 0.5 < ΔEN < 1.7 in covalent sharing. A tempting distractor is nonpolar covalent, but it is incorrect due to the ΔEN, misconceptions come from confusing molecular polarity with bond polarity. Distinguish bond types by focusing on individual bond ΔEN, not overall molecule symmetry.

Question 7

In $\mathrm{F_2(g)}$ , each F atom has electronegativity 4.0, so $\Delta EN = 0.0$ for the F–F bond. Which classification best describes the bond in $\mathrm{F_2}$ ?

Polar covalent bond
Metallic bond
Ionic bond
London dispersion force
Nonpolar covalent bond (correct answer)

Explanation: This question tests the skill of identifying bond types when identical atoms bond. In F₂, both fluorine atoms have the same electronegativity (4.0), resulting in ΔEN = 0, which definitively indicates a nonpolar covalent bond. The electrons in the F-F bond are shared perfectly equally because neither atom can attract electrons more strongly than the other. Students might incorrectly choose polar covalent bond (C) by focusing on fluorine's extremely high electronegativity value, but polarity requires different atoms with different electronegativities. Remember that bonds between identical atoms are always nonpolar covalent, regardless of how electronegative those atoms are.

Question 8

In $\mathrm{NH_3(g)}$ , the electronegativity of N is 3.0 and that of H is 2.1, giving $\Delta EN = 0.9$ . Which classification best describes an N–H bond in ammonia?

Ionic bond
Polar covalent bond (correct answer)
Nonpolar covalent bond
Metallic bond
Hydrogen bond

Explanation: This question tests the skill of classifying bonds based on electronegativity differences. The electronegativity difference between N and H is 0.9, which falls in the range of 0.4 to 1.7, indicating a polar covalent bond. In NH₃, nitrogen's higher electronegativity causes it to attract the shared electrons more strongly than hydrogen, creating partial charges and making each N-H bond polar. Students might incorrectly choose nonpolar covalent bond (C) by underestimating the effect of a 0.9 electronegativity difference, but this clearly exceeds the 0.4 threshold for polarity. When ΔEN falls between 0.4 and 1.7, the bond is polar covalent with unequal electron sharing.

Question 9

A bond forms between nitrogen and oxygen in NO. The electronegativity values are approximately $EN(\text{N})=3.0$ and $EN(\text{O})=3.4$ , so $\Delta EN \approx 0.4$ . Which classification best describes the N–O bond?

Nonpolar covalent
Polar covalent (correct answer)
Ionic
Metallic
London dispersion

Explanation: This question tests the skill of classifying chemical bonds based on electronegativity differences. The N-O bond has ΔEN = 3.4 - 3.0 = 0.4, indicating unequal electron sharing that creates a polar covalent bond. Despite the relatively small electronegativity difference, oxygen's higher electronegativity causes electrons to spend more time near the O atom, creating partial charges (δ+ on N and δ- on O). This unequal distribution distinguishes polar covalent bonds from nonpolar ones. Students might incorrectly choose nonpolar covalent (A), thinking the small ΔEN makes the bond nonpolar, but any measurable electronegativity difference creates polarity in the bond. Remember that polar covalent bonds exist whenever 0 < ΔEN < 1.7, regardless of how small the difference might be.

Question 10

In carbon dioxide, one C–O bond has $\chi_\text{C}=2.5$ and $\chi_\text{O}=3.5$ (so $\Delta\chi\approx1.0$ ). Which best classifies each C–O bond in CO $_2$ ?

Nonpolar covalent
Ionic
Polar covalent (correct answer)
Metallic
Dipole–dipole attraction

Explanation: This question tests the skill of classifying bonds based on electronegativity differences between nonmetal atoms. The C-O bond has an electronegativity difference of 1.0, which falls within the range of 0.4 to 1.7, characteristic of polar covalent bonds. In polar covalent bonds, electrons are shared between atoms but unequally, with oxygen (the more electronegative atom) pulling electron density toward itself, creating a partial negative charge on O and partial positive charge on C. The bond is not ionic because both elements are nonmetals and the electronegativity difference is less than 1.7. Students might incorrectly choose nonpolar covalent (A), perhaps thinking all bonds between nonmetals are nonpolar, but the significant electronegativity difference creates polarity. To classify covalent bonds correctly, always check the electronegativity difference: bonds between nonmetals with 0.4 ≤ Δχ < 1.7 are polar covalent.