,CHEM 121 Module 3 Exam Foundations of General
Chemistry w/Lab | Portage | 26/27 Actual (PDF)
1. Which type of bond is formed when one atom donates electrons to another, resulting in the
formation of oppositely charged ions?
A) Covalent bond
B) Ionic bond
C) Metallic bond
D) Hydrogen bond
Correct Answer: Ionic bond
Rationale: Ionic bonds form through the complete transfer of electrons from a metal to a nonmetal,
creating cations and anions that attract electrostatically. Covalent bonds involve electron sharing,
metallic bonds involve delocalized electrons, and hydrogen bonds are intermolecular forces. Options
A, C, and D describe different bonding mechanisms.
2. Which element is most likely to form a cation with a +2 charge?
A) Sodium
B) Magnesium
C) Chlorine
D) Oxygen
Correct Answer: Magnesium
Rationale: Magnesium has two valence electrons and readily loses them to achieve a noble gas
configuration, forming Mg²⁺. Sodium forms a +1 cation, chlorine forms a -1 anion, and oxygen forms a
-2 anion. Options A, C, and D describe different ion formation tendencies.
,3. What is the correct name for the ionic compound formed between potassium and sulfur?
A) Potassium sulfide
B) Dipotassium sulfide
C) Potassium sulfur
D) Potassium(II) sulfide
Correct Answer: Potassium sulfide
Rationale: Potassium forms a +1 cation and sulfide is the S²⁻ anion, so the compound is K₂S, named
potassium sulfide. Roman numerals are not used because potassium has a fixed oxidation state.
Options B, C, and D use incorrect naming conventions.
4. Which of the following represents the correct Lewis symbol for a nitrogen atom?
A) :N·
B) ·N:
C) ·N·
D) :N:
Correct Answer: ·N·
Rationale: Nitrogen has five valence electrons, so its Lewis symbol shows the element symbol
surrounded by five dots, typically arranged as one pair and three unpaired dots. Option A shows four
electrons, option C shows three, and option D shows six. Options A, C, and D have incorrect electron
counts.
5. What is the molecular geometry of a molecule with four bonding pairs and no lone pairs on the
central atom?
A) Tetrahedral
, B) Trigonal planar
C) Bent
D) Linear
Correct Answer: Tetrahedral
Rationale: According to VSEPR theory, four bonding pairs arrange themselves as far apart as possible
in a tetrahedral geometry with bond angles of 109.5°. Trigonal planar has three bonding pairs, bent
has lone pairs, and linear has two bonding pairs. Options B, C, and D describe different electron
domain geometries.
6. Which intermolecular force is present in all molecules, regardless of polarity?
A) Hydrogen bonding
B) Dipole-dipole interactions
C) London dispersion forces
D) Ion-dipole interactions
Correct Answer: London dispersion forces
Rationale: London dispersion forces arise from temporary fluctuations in electron density and are
present in all molecules, though they are strongest in large, polarizable molecules. Hydrogen bonding
and dipole-dipole require specific polar groups, and ion-dipole requires ions. Options A, B, and D are
not universal.
7. What is the formal charge on the central oxygen atom in a water molecule (H₂O)?
A) 0
B) +1
C) -1
D) +2
Chemistry w/Lab | Portage | 26/27 Actual (PDF)
1. Which type of bond is formed when one atom donates electrons to another, resulting in the
formation of oppositely charged ions?
A) Covalent bond
B) Ionic bond
C) Metallic bond
D) Hydrogen bond
Correct Answer: Ionic bond
Rationale: Ionic bonds form through the complete transfer of electrons from a metal to a nonmetal,
creating cations and anions that attract electrostatically. Covalent bonds involve electron sharing,
metallic bonds involve delocalized electrons, and hydrogen bonds are intermolecular forces. Options
A, C, and D describe different bonding mechanisms.
2. Which element is most likely to form a cation with a +2 charge?
A) Sodium
B) Magnesium
C) Chlorine
D) Oxygen
Correct Answer: Magnesium
Rationale: Magnesium has two valence electrons and readily loses them to achieve a noble gas
configuration, forming Mg²⁺. Sodium forms a +1 cation, chlorine forms a -1 anion, and oxygen forms a
-2 anion. Options A, C, and D describe different ion formation tendencies.
,3. What is the correct name for the ionic compound formed between potassium and sulfur?
A) Potassium sulfide
B) Dipotassium sulfide
C) Potassium sulfur
D) Potassium(II) sulfide
Correct Answer: Potassium sulfide
Rationale: Potassium forms a +1 cation and sulfide is the S²⁻ anion, so the compound is K₂S, named
potassium sulfide. Roman numerals are not used because potassium has a fixed oxidation state.
Options B, C, and D use incorrect naming conventions.
4. Which of the following represents the correct Lewis symbol for a nitrogen atom?
A) :N·
B) ·N:
C) ·N·
D) :N:
Correct Answer: ·N·
Rationale: Nitrogen has five valence electrons, so its Lewis symbol shows the element symbol
surrounded by five dots, typically arranged as one pair and three unpaired dots. Option A shows four
electrons, option C shows three, and option D shows six. Options A, C, and D have incorrect electron
counts.
5. What is the molecular geometry of a molecule with four bonding pairs and no lone pairs on the
central atom?
A) Tetrahedral
, B) Trigonal planar
C) Bent
D) Linear
Correct Answer: Tetrahedral
Rationale: According to VSEPR theory, four bonding pairs arrange themselves as far apart as possible
in a tetrahedral geometry with bond angles of 109.5°. Trigonal planar has three bonding pairs, bent
has lone pairs, and linear has two bonding pairs. Options B, C, and D describe different electron
domain geometries.
6. Which intermolecular force is present in all molecules, regardless of polarity?
A) Hydrogen bonding
B) Dipole-dipole interactions
C) London dispersion forces
D) Ion-dipole interactions
Correct Answer: London dispersion forces
Rationale: London dispersion forces arise from temporary fluctuations in electron density and are
present in all molecules, though they are strongest in large, polarizable molecules. Hydrogen bonding
and dipole-dipole require specific polar groups, and ion-dipole requires ions. Options A, B, and D are
not universal.
7. What is the formal charge on the central oxygen atom in a water molecule (H₂O)?
A) 0
B) +1
C) -1
D) +2
