Electronegativity: Mastery Test

Select the correct answer. Which pair of molecules is not a polar bond?

• N - O

• C - O

• O - H

• O - O

Answer explanation

The O - O bond is nonpolar because it involves two identical oxygen atoms sharing electrons equally. In contrast, the other pairs (N - O, C - O, O - H) involve different electronegativities, resulting in polar bonds.

Use the chart to determine which pair of atoms has the greatest difference in electronegativity.

• Ca - Cl

• H - Cl

• Fe - Cl

• P - Cl

Answer explanation

The electronegativity difference between H (2.20) and Cl (3.16) is 0.96, which is greater than the differences for the other pairs. Therefore, H - Cl has the greatest difference in electronegativity.

Use the chart to determine which type of bond is formed between potassium (K) and chlorine (Cl).

• nonpolar covalent

• moderately polar covalent

• highly polar covalent

• ionic

Answer explanation

The bond between potassium (K) and chlorine (Cl) is ionic because potassium is a metal that donates an electron, while chlorine is a nonmetal that accepts an electron, resulting in the formation of oppositely charged ions.

Select the correct answer. Use the chart to determine which is an example of a highly polar covalent bond.

• Ca – Cl

• Fe – O

• H – S

• F – F

Answer explanation

The Fe – O bond is highly polar due to the significant difference in electronegativity between iron (Fe) and oxygen (O). This results in a strong dipole moment, making it a classic example of a highly polar covalent bond.

Select the correct answer. The elements found in Group 2A, from top to bottom, include beryllium, magnesium, calcium, strontium, and barium. Which of these elements has the highest electronegativity value?

• beryllium

• magnesium

• calcium

• barium

Answer explanation

Beryllium has the highest electronegativity value among the Group 2A elements. As you move down the group, electronegativity decreases due to increased atomic size and shielding effect, making beryllium the most electronegative.

Select the correct answer. Use the chart to determine which pairs of atoms are arranged in the correct order according to increasing bond polarity.

• H – Cl < H – F < H – O < H – S

• H – S < H – Cl < H – O < H – F

• H – O < H – S < H – Cl < H – F

• H – F < H – O < H – Cl < H – S

Answer explanation

The correct order of increasing bond polarity is determined by the electronegativity of the atoms. H – S has the lowest polarity, followed by H – Cl, H – O, and H – F, which has the highest polarity.

Select the correct answer. Use the chart to determine which atom in the carbon–chlorine bond is assigned the delta negative charge.

• carbon atom

• chlorine atom

• neither atom

• both atoms

Answer explanation

In a carbon–chlorine bond, chlorine is more electronegative than carbon, meaning it attracts the shared electrons more strongly. This results in the chlorine atom being assigned a delta negative charge.

Select the correct answer. Which statement is true?

• A molecule having a covalent bond can be ionic.

• A molecule having a covalent bond is always polar.

• A molecule having a covalent bond may be polar or nonpolar.

• A molecule having a covalent bond is always nonpolar.

Answer explanation

A molecule with a covalent bond can be either polar or nonpolar, depending on the electronegativity of the atoms involved and the molecular geometry. Thus, the correct statement is that a molecule having a covalent bond may be polar or nonpolar.

Select the correct answer. The molecule hydrogen fluoride (HF) contains a polar bond H – F, where fluorine is more electronegative than hydrogen. Which is the appropriate representation of the H – F bond?

• H – F⁺

• H⁺ – F⁻

• δ⁺H – Fδ⁺

• δ⁺H – Fδ⁻

Answer explanation

The H – F bond is polar due to the difference in electronegativity. Fluorine is more electronegative, attracting electrons more strongly, resulting in a partial negative charge (δ⁻) on F and a partial positive charge (δ⁺) on H. Thus, the correct representation is δ⁺H – Fδ⁻.