ACS Chemistry General Exam 2026 |
Complete Questions and Guide Answers,
100% Verified Graded A+
Question 1
Which particle determines the identity of an element?
A) Electron
B) Neutron
C) Proton
D) Nucleus
Correct Answer: C
Rationale: The number of protons in an atom's nucleus defines the atomic number
(Z), which uniquely identifies an element. Changing the number of protons changes
the element itself, while electrons and neutrons can vary without altering elemental
identity.
Question 2
What is the correct electron configuration for oxygen (Z = 8)?
A) 1s² 2s² 2p⁴
B) 1s² 2s² 2p⁶
C) 1s² 2p⁶
D) 1s² 2s² 2p³
Correct Answer: A
,Rationale: Oxygen has 8 electrons. Filling orbitals in order of increasing energy
(Aufbau principle) gives 1s² (2 electrons), 2s² (2 electrons), and 2p⁴ (4 electrons).
This configuration follows Hund's rule and the Pauli exclusion principle.
Question 3
What are the allowed values of the principal quantum number (n)?
A) 0, 1, 2, 3, ...
B) 1, 2, 3, 4, ...
C) -n to +n
D) Any positive or negative integer
Correct Answer: B
Rationale: The principal quantum number (n) can be any positive integer from 1 to
infinity. It indicates the energy level and relative size of the orbital.
Question 4
What are the allowed values of the azimuthal (angular momentum) quantum
number (l)?
A) 1, 2, 3, ..., n
B) 0, 1, 2, ..., n-1
C) -l to +l
D) 0 or 1 only
Correct Answer: B
,Rationale: The azimuthal quantum number (l) can have values from 0 up to n-1. It
determines the shape of the orbital (s, p, d, f).
Question 5
What are the allowed values of the magnetic quantum number (m_l)?
A) 0 to n-1
B) -l to +l
C) -n to +n
D) +1/2 or -1/2
Correct Answer: B
Rationale: The magnetic quantum number (m_l) can have integer values from -l to
+l, including zero. It determines the orientation of the orbital in space.
Question 6
Which set of quantum numbers is incorrect?
A) n=3, l=2, m_l=-1, m_s=+1/2
B) n=4, l=0, m_l=-1, m_s=+1/2
C) n=3, l=1, m_l=-1, m_s=+1/2
D) n=4, l=0, m_l=0, m_s=+1/2
Correct Answer: B
Rationale: For l=0, the only allowed value of m_l is 0. Option B has m_l=-1, which is
not allowed for l=0. All other options have valid quantum numbers.
, Question 7
What type of electron is described by the quantum numbers n=3, l=2, m_l=1,
m_s=+1/2?
A) 3s electron
B) 3p electron
C) 3d electron
D) 3f electron
Correct Answer: C
Rationale: n=3 indicates the third energy level, and l=2 corresponds to a d orbital.
Therefore, this is a 3d electron.
Question 8
What is the electron configuration of the valence electrons for a ground-state Ge
atom?
A) 4s²4p²
B) 4s²4p⁴
C) 3d¹⁰4s²4p²
D) 4s²3d¹⁰4p²
Correct Answer: A
Rationale: Germanium (Ge) has atomic number 32. Its electron configuration is
[Ar]3d¹⁰4s²4p². The valence electrons are the 4s²4p² electrons.
Complete Questions and Guide Answers,
100% Verified Graded A+
Question 1
Which particle determines the identity of an element?
A) Electron
B) Neutron
C) Proton
D) Nucleus
Correct Answer: C
Rationale: The number of protons in an atom's nucleus defines the atomic number
(Z), which uniquely identifies an element. Changing the number of protons changes
the element itself, while electrons and neutrons can vary without altering elemental
identity.
Question 2
What is the correct electron configuration for oxygen (Z = 8)?
A) 1s² 2s² 2p⁴
B) 1s² 2s² 2p⁶
C) 1s² 2p⁶
D) 1s² 2s² 2p³
Correct Answer: A
,Rationale: Oxygen has 8 electrons. Filling orbitals in order of increasing energy
(Aufbau principle) gives 1s² (2 electrons), 2s² (2 electrons), and 2p⁴ (4 electrons).
This configuration follows Hund's rule and the Pauli exclusion principle.
Question 3
What are the allowed values of the principal quantum number (n)?
A) 0, 1, 2, 3, ...
B) 1, 2, 3, 4, ...
C) -n to +n
D) Any positive or negative integer
Correct Answer: B
Rationale: The principal quantum number (n) can be any positive integer from 1 to
infinity. It indicates the energy level and relative size of the orbital.
Question 4
What are the allowed values of the azimuthal (angular momentum) quantum
number (l)?
A) 1, 2, 3, ..., n
B) 0, 1, 2, ..., n-1
C) -l to +l
D) 0 or 1 only
Correct Answer: B
,Rationale: The azimuthal quantum number (l) can have values from 0 up to n-1. It
determines the shape of the orbital (s, p, d, f).
Question 5
What are the allowed values of the magnetic quantum number (m_l)?
A) 0 to n-1
B) -l to +l
C) -n to +n
D) +1/2 or -1/2
Correct Answer: B
Rationale: The magnetic quantum number (m_l) can have integer values from -l to
+l, including zero. It determines the orientation of the orbital in space.
Question 6
Which set of quantum numbers is incorrect?
A) n=3, l=2, m_l=-1, m_s=+1/2
B) n=4, l=0, m_l=-1, m_s=+1/2
C) n=3, l=1, m_l=-1, m_s=+1/2
D) n=4, l=0, m_l=0, m_s=+1/2
Correct Answer: B
Rationale: For l=0, the only allowed value of m_l is 0. Option B has m_l=-1, which is
not allowed for l=0. All other options have valid quantum numbers.
, Question 7
What type of electron is described by the quantum numbers n=3, l=2, m_l=1,
m_s=+1/2?
A) 3s electron
B) 3p electron
C) 3d electron
D) 3f electron
Correct Answer: C
Rationale: n=3 indicates the third energy level, and l=2 corresponds to a d orbital.
Therefore, this is a 3d electron.
Question 8
What is the electron configuration of the valence electrons for a ground-state Ge
atom?
A) 4s²4p²
B) 4s²4p⁴
C) 3d¹⁰4s²4p²
D) 4s²3d¹⁰4p²
Correct Answer: A
Rationale: Germanium (Ge) has atomic number 32. Its electron configuration is
[Ar]3d¹⁰4s²4p². The valence electrons are the 4s²4p² electrons.
