Portage Learning CHEM 103 General
Chemistry I Module 5 Exam
,Portage Learning CHEM 103 General
Chemistry I Module 5 Exam
Question 1
An element with atomic number \(Z = 3\) forms a stable ion. What is the charge and
electronic configuration of this ion?
A) \(-1\), \(1s^{2}2s^{2}\)
B) \(+1\), \(1s^{2}2s^{1}\)
C) \(+1\), \(1s^{2}\)
D) \(-1\), \(1s^{2}\)
Answer: C
Rationale: Atomic number 3 is Lithium (Li). Its neutral ground-state configuration is
\(1s^{2}2s^{1}\). As a Group 1 alkali metal, it achieves a stable valence shell by losing
its single 2s valence electron to become isoelectronic with the noble gas Helium,
forming a \(Li^{+}\) cation with a stable \(1s^{2}\) configuration.
Question 2
Which of the following electron configurations belongs to a stable oxide ion?
A) \(1s^{2}2s^{2}2p^{4}\)
B) \(1s^{2}2s^{2}2p^{6}\)
C) \(1s^{2}2s^{2}2p^{2}\)
D) \(1s^{2}2s^{2}\)
Answer: B
Rationale: Oxygen (\(Z = 8\)) has a neutral configuration of \(1s^{2}2s^{2}2p^{4}\). To
satisfy the octet rule, it gains 2 electrons into its 2p subshell to achieve a full valence
shell. This forms the \(O^{2-}\) anion with a stable configuration of
\(1s^{2}2s^{2}2p^{6}\), which is isoelectronic with Neon.
Question 3
How many total valence electrons are available to construct the Lewis structure for the
sulfate ion (\(SO_{4}^{2-}\))?
A) 30
, Portage Learning CHEM 103 General
Chemistry I Module 5 Exam
B) 32
C) 26
D) 28
Answer: B
Rationale: Sulfur contributes 6 valence electrons (\(1 \times 6 = 6\)). Each Oxygen
contributes 6 valence electrons (\(4 \times 6 = 24\)). The \(-2\) net charge indicates the
addition of 2 extra electrons (\(+2\)). Summing these yields: \(6 + 24 + 2 = 32\) total
valence electrons.
Question 4
Using electronegativity trends, which of the following bonds is classified as nonpolar
covalent?
A) \(N - H\)
B) \(O - H\)
C) \(C - H\)
D) \(Li - F\)
Answer: C
Rationale: A bond is nonpolar covalent when the electronegativity difference (\(\Delta
\)EN) is less than 0.5. The difference between Carbon (2.5) and Hydrogen (2.1) is
\(\Delta\text{EN} = 0.4\), making it nonpolar. \(N-H\) and \(O-H\) have larger differences
and are polar covalent, while \(Li-F\) is purely ionic.
Question 5
According to VSEPR theory, what is the molecular geometry of a molecule with 2
bonding pairs and 2 lone pairs on the central atom?
A) Linear
B) Bent
C) Tetrahedral
D) Trigonal Planar
Answer: B
Rationale: An atom surrounded by 4 total electron domains (2 bonding pairs, 2 lone
pairs) has a tetrahedral electron-pair geometry. Because the 2 lone pairs occupy space
Chemistry I Module 5 Exam
,Portage Learning CHEM 103 General
Chemistry I Module 5 Exam
Question 1
An element with atomic number \(Z = 3\) forms a stable ion. What is the charge and
electronic configuration of this ion?
A) \(-1\), \(1s^{2}2s^{2}\)
B) \(+1\), \(1s^{2}2s^{1}\)
C) \(+1\), \(1s^{2}\)
D) \(-1\), \(1s^{2}\)
Answer: C
Rationale: Atomic number 3 is Lithium (Li). Its neutral ground-state configuration is
\(1s^{2}2s^{1}\). As a Group 1 alkali metal, it achieves a stable valence shell by losing
its single 2s valence electron to become isoelectronic with the noble gas Helium,
forming a \(Li^{+}\) cation with a stable \(1s^{2}\) configuration.
Question 2
Which of the following electron configurations belongs to a stable oxide ion?
A) \(1s^{2}2s^{2}2p^{4}\)
B) \(1s^{2}2s^{2}2p^{6}\)
C) \(1s^{2}2s^{2}2p^{2}\)
D) \(1s^{2}2s^{2}\)
Answer: B
Rationale: Oxygen (\(Z = 8\)) has a neutral configuration of \(1s^{2}2s^{2}2p^{4}\). To
satisfy the octet rule, it gains 2 electrons into its 2p subshell to achieve a full valence
shell. This forms the \(O^{2-}\) anion with a stable configuration of
\(1s^{2}2s^{2}2p^{6}\), which is isoelectronic with Neon.
Question 3
How many total valence electrons are available to construct the Lewis structure for the
sulfate ion (\(SO_{4}^{2-}\))?
A) 30
, Portage Learning CHEM 103 General
Chemistry I Module 5 Exam
B) 32
C) 26
D) 28
Answer: B
Rationale: Sulfur contributes 6 valence electrons (\(1 \times 6 = 6\)). Each Oxygen
contributes 6 valence electrons (\(4 \times 6 = 24\)). The \(-2\) net charge indicates the
addition of 2 extra electrons (\(+2\)). Summing these yields: \(6 + 24 + 2 = 32\) total
valence electrons.
Question 4
Using electronegativity trends, which of the following bonds is classified as nonpolar
covalent?
A) \(N - H\)
B) \(O - H\)
C) \(C - H\)
D) \(Li - F\)
Answer: C
Rationale: A bond is nonpolar covalent when the electronegativity difference (\(\Delta
\)EN) is less than 0.5. The difference between Carbon (2.5) and Hydrogen (2.1) is
\(\Delta\text{EN} = 0.4\), making it nonpolar. \(N-H\) and \(O-H\) have larger differences
and are polar covalent, while \(Li-F\) is purely ionic.
Question 5
According to VSEPR theory, what is the molecular geometry of a molecule with 2
bonding pairs and 2 lone pairs on the central atom?
A) Linear
B) Bent
C) Tetrahedral
D) Trigonal Planar
Answer: B
Rationale: An atom surrounded by 4 total electron domains (2 bonding pairs, 2 lone
pairs) has a tetrahedral electron-pair geometry. Because the 2 lone pairs occupy space
