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HESI A2 CHEMISTRY EXAM 2026 COMPLETE
(151) CURRENT TESTING QUESTIONS AND
CORRECT ANSWERS WITH DETAILED
EXPLANATIONS|GUARANTEED PASS.
CHEMISTRY
Master the HESI A2 Chemistry Exam using focused questions on atomic
structure, chemical bonding, stoichiometry, solutions and
concentrations, acids and bases, reaction types, and fundamental
periodic trends. This resource strengthens your grasp of essential
nursing entrance chemistry concepts and problem-solving strategies.
Ideal for reinforcing core knowledge and sharpening test-taking speed
for this critical admission exam. Perfect for pre-nursing students, allied
health applicants, and anyone aiming to achieve a competitive HESI A2
chemistry score.
Multiple choice.
SECTION 1: ATOMIC STRUCTURE (Questions 1-20)
Question 1
What is the maximum number of electrons that can occupy the third principal energy level
(n=3)?
A) 8
B) 10
C) 18
D) 32
Correct Answer: C) 18
Rationale: The maximum number of electrons in any principal energy level is given by 2n².
For n=3, 2(3)² = 2(9) = 18 electrons. The third energy level contains s, p, and d subshells
(3s², 3p⁶, 3d¹⁰ = total 18).
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Question 2
Which subatomic particle has a relative mass of approximately 1 amu and a positive
charge?
A) Electron
B) Neutron
C) Proton
D) Positron
Correct Answer: C) Proton
Rationale: Protons have a mass of approximately 1 atomic mass unit (1.0073 amu) and a
charge of +1. Neutrons have similar mass but no charge. Electrons have negligible mass
(1/1836 amu) and negative charge.
Question 3
An atom has 17 protons, 18 neutrons, and 17 electrons. What is its mass number?
A) 17
B) 34
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C) 35
D) 52
Correct Answer: C) 35
Rationale: Mass number = number of protons + number of neutrons = 17 + 18 = 35. The
number of electrons does not affect mass number. This atom is chlorine-35, an isotope of
chlorine.
Question 4
Which of the following represents an isotope of carbon-12?
A) Carbon atom with 6 protons, 6 neutrons
B) Carbon atom with 6 protons, 7 neutrons
C) Carbon atom with 6 protons, 8 electrons
D) Carbon atom with 7 protons, 6 neutrons
Correct Answer: B) Carbon atom with 6 protons, 7 neutrons
Rationale: Isotopes are atoms of the same element with the same number of protons but
different numbers of neutrons. Carbon-12 has 6 protons, 6 neutrons. Carbon-13 has 6
protons, 7 neutrons, making it an isotope of carbon-12.
Question 5
What is the electron configuration of sodium (atomic number 11)?
A) 1s² 2s² 2p⁶ 3s¹
B) 1s² 2s² 2p⁶ 3s²
C) 1s² 2s² 2p⁶ 3p¹
D) 1s² 2s² 2p⁶ 3d¹
Correct Answer: A) 1s² 2s² 2p⁶ 3s¹
Rationale: Sodium has 11 electrons. The order of filling is 1s, 2s, 2p, 3s (Aufbau principle).
1s² (2 e⁻), 2s² (4 e⁻ total), 2p⁶ (10 e⁻ total), 3s¹ (11th electron).
Question 6
Which quantum number describes the shape of an orbital?
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A) Principal quantum number (n)
B) Angular momentum quantum number (l)
C) Magnetic quantum number (m𝖫)
D) Spin quantum number (mₛ)
Correct Answer: B) Angular momentum quantum number (l)
Rationale: The angular momentum quantum number (l) determines the shape of the
orbital (s = spherical, p = dumbbell, d = cloverleaf, etc.). The principal quantum number (n)
determines energy level and size. The magnetic quantum number (m𝖫) determines orbital
orientation.
Question 7
How many orbitals are in the d subshell?
A) 3
B) 5
C) 7
D) 9
Correct Answer: B) 5
Rationale: The d subshell has an angular momentum quantum number l=2. The number of
orbitals in a subshell = 2l + 1 = 2(2) + 1 = 5 orbitals (dxy, dxz, dyz, dx²-y², dz²).
Question 8
Which of the following atoms has the largest atomic radius?
A) Lithium (Li)
B) Beryllium (Be)
C) Boron (B)
D) Carbon (C)
Correct Answer: A) Lithium (Li)
Rationale: Atomic radius decreases from left to right across a period due to increasing
nuclear charge pulling electrons closer. Lithium is furthest left in period 2, so it has the
largest atomic radius among these options.
HESI A2 CHEMISTRY EXAM 2026 COMPLETE
(151) CURRENT TESTING QUESTIONS AND
CORRECT ANSWERS WITH DETAILED
EXPLANATIONS|GUARANTEED PASS.
CHEMISTRY
Master the HESI A2 Chemistry Exam using focused questions on atomic
structure, chemical bonding, stoichiometry, solutions and
concentrations, acids and bases, reaction types, and fundamental
periodic trends. This resource strengthens your grasp of essential
nursing entrance chemistry concepts and problem-solving strategies.
Ideal for reinforcing core knowledge and sharpening test-taking speed
for this critical admission exam. Perfect for pre-nursing students, allied
health applicants, and anyone aiming to achieve a competitive HESI A2
chemistry score.
Multiple choice.
SECTION 1: ATOMIC STRUCTURE (Questions 1-20)
Question 1
What is the maximum number of electrons that can occupy the third principal energy level
(n=3)?
A) 8
B) 10
C) 18
D) 32
Correct Answer: C) 18
Rationale: The maximum number of electrons in any principal energy level is given by 2n².
For n=3, 2(3)² = 2(9) = 18 electrons. The third energy level contains s, p, and d subshells
(3s², 3p⁶, 3d¹⁰ = total 18).
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Question 2
Which subatomic particle has a relative mass of approximately 1 amu and a positive
charge?
A) Electron
B) Neutron
C) Proton
D) Positron
Correct Answer: C) Proton
Rationale: Protons have a mass of approximately 1 atomic mass unit (1.0073 amu) and a
charge of +1. Neutrons have similar mass but no charge. Electrons have negligible mass
(1/1836 amu) and negative charge.
Question 3
An atom has 17 protons, 18 neutrons, and 17 electrons. What is its mass number?
A) 17
B) 34
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C) 35
D) 52
Correct Answer: C) 35
Rationale: Mass number = number of protons + number of neutrons = 17 + 18 = 35. The
number of electrons does not affect mass number. This atom is chlorine-35, an isotope of
chlorine.
Question 4
Which of the following represents an isotope of carbon-12?
A) Carbon atom with 6 protons, 6 neutrons
B) Carbon atom with 6 protons, 7 neutrons
C) Carbon atom with 6 protons, 8 electrons
D) Carbon atom with 7 protons, 6 neutrons
Correct Answer: B) Carbon atom with 6 protons, 7 neutrons
Rationale: Isotopes are atoms of the same element with the same number of protons but
different numbers of neutrons. Carbon-12 has 6 protons, 6 neutrons. Carbon-13 has 6
protons, 7 neutrons, making it an isotope of carbon-12.
Question 5
What is the electron configuration of sodium (atomic number 11)?
A) 1s² 2s² 2p⁶ 3s¹
B) 1s² 2s² 2p⁶ 3s²
C) 1s² 2s² 2p⁶ 3p¹
D) 1s² 2s² 2p⁶ 3d¹
Correct Answer: A) 1s² 2s² 2p⁶ 3s¹
Rationale: Sodium has 11 electrons. The order of filling is 1s, 2s, 2p, 3s (Aufbau principle).
1s² (2 e⁻), 2s² (4 e⁻ total), 2p⁶ (10 e⁻ total), 3s¹ (11th electron).
Question 6
Which quantum number describes the shape of an orbital?
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A) Principal quantum number (n)
B) Angular momentum quantum number (l)
C) Magnetic quantum number (m𝖫)
D) Spin quantum number (mₛ)
Correct Answer: B) Angular momentum quantum number (l)
Rationale: The angular momentum quantum number (l) determines the shape of the
orbital (s = spherical, p = dumbbell, d = cloverleaf, etc.). The principal quantum number (n)
determines energy level and size. The magnetic quantum number (m𝖫) determines orbital
orientation.
Question 7
How many orbitals are in the d subshell?
A) 3
B) 5
C) 7
D) 9
Correct Answer: B) 5
Rationale: The d subshell has an angular momentum quantum number l=2. The number of
orbitals in a subshell = 2l + 1 = 2(2) + 1 = 5 orbitals (dxy, dxz, dyz, dx²-y², dz²).
Question 8
Which of the following atoms has the largest atomic radius?
A) Lithium (Li)
B) Beryllium (Be)
C) Boron (B)
D) Carbon (C)
Correct Answer: A) Lithium (Li)
Rationale: Atomic radius decreases from left to right across a period due to increasing
nuclear charge pulling electrons closer. Lithium is furthest left in period 2, so it has the
largest atomic radius among these options.
