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HESI A2 Chemistry Exam Bank: Atomic
Structure, Elements, and Bonding
Table of Contents
Subtopic 1: Atomic Structure and Properties of Subatomic Particles...............2
Subtopic 2: Electron Configuration and Periodic Trends...................................8
Subtopic 3: Chemical Bonds and Molecular Structure...................................15
Subtopic 4: Periodic Table Structure and Classification of Elements..............22
Subtopic 5: Chemical Reactions and Conservation of Mass...........................28
Subtopic 6: Oxidation, Reduction, and Redox Reactions................................35
Subtopic 7: Acids, Bases, and pH as Related to Bonding and Ions.................42
Subtopic 8: Atomic Theory and Models of the Atom......................................49
Subtopic 9: Chemical Bonds and Molecular Geometry..................................55
Subtopic 10: Energy in Chemical Bonds and Reactions.................................62
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Subtopic 1: Atomic Structure and Properties of
Subatomic Particles
(Questions 1–20)
1. Which subatomic particle is responsible for the identity of an element?
A. Neutron
B. Electron
C. Proton
D. Quark
Correct answer: C
Rationale: The number of protons (atomic number) defines an element. For
example, all atoms with 6 protons are carbon atoms.
2. What is the relative charge of a neutron?
A. +1
B. –1
C. 0
D. –2
Correct answer: C
Rationale: Neutrons are electrically neutral particles found in the nucleus,
balancing the positively charged protons.
3. The atomic number of an element refers to the number of:
A. Neutrons
B. Electrons in the outer shell
C. Protons in the nucleus
, 3
D. Total subatomic particles
Correct answer: C
Rationale: The atomic number is the number of protons in the nucleus, which
determines the chemical properties of an element.
4. Which subatomic particle determines the chemical behavior of an atom?
A. Neutron
B. Electron
C. Proton
D. Nucleon
Correct answer: B
Rationale: Electrons, particularly valence electrons, determine how atoms
bond and react with others.
5. An atom has 11 protons, 12 neutrons, and 11 electrons. What is the
atomic mass?
A. 11
B. 12
C. 22
D. 23
Correct answer: D
Rationale: Atomic mass ≈ number of protons + number of neutrons = 11 +
12 = 23.
6. Which of the following best describes isotopes?
A. Atoms with different numbers of electrons
B. Atoms with the same number of protons but different numbers of neutrons
C. Atoms with different numbers of protons
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D. Atoms with different atomic numbers
Correct answer: B
Rationale: Isotopes are forms of the same element (same protons) with
differing neutrons, affecting atomic mass.
7. What is the mass of an electron compared to a proton?
A. Equal
B. 10 times larger
C. 1/10th of a proton
D. Approximately 1/1836th of a proton
Correct answer: D
Rationale: Electrons are significantly lighter than protons and neutrons,
almost negligible in atomic mass.
8. Which part of the atom contains the most mass?
A. Electron cloud
B. Orbitals
C. Nucleus
D. Shells
Correct answer: C
Rationale: The nucleus, composed of protons and neutrons, accounts for
nearly all the atom’s mass.
9. What is the charge of an atom with 9 protons and 10 electrons?
A. +1
B. Neutral
C. –1
D. –2
HESI A2 Chemistry Exam Bank: Atomic
Structure, Elements, and Bonding
Table of Contents
Subtopic 1: Atomic Structure and Properties of Subatomic Particles...............2
Subtopic 2: Electron Configuration and Periodic Trends...................................8
Subtopic 3: Chemical Bonds and Molecular Structure...................................15
Subtopic 4: Periodic Table Structure and Classification of Elements..............22
Subtopic 5: Chemical Reactions and Conservation of Mass...........................28
Subtopic 6: Oxidation, Reduction, and Redox Reactions................................35
Subtopic 7: Acids, Bases, and pH as Related to Bonding and Ions.................42
Subtopic 8: Atomic Theory and Models of the Atom......................................49
Subtopic 9: Chemical Bonds and Molecular Geometry..................................55
Subtopic 10: Energy in Chemical Bonds and Reactions.................................62
, 2
Subtopic 1: Atomic Structure and Properties of
Subatomic Particles
(Questions 1–20)
1. Which subatomic particle is responsible for the identity of an element?
A. Neutron
B. Electron
C. Proton
D. Quark
Correct answer: C
Rationale: The number of protons (atomic number) defines an element. For
example, all atoms with 6 protons are carbon atoms.
2. What is the relative charge of a neutron?
A. +1
B. –1
C. 0
D. –2
Correct answer: C
Rationale: Neutrons are electrically neutral particles found in the nucleus,
balancing the positively charged protons.
3. The atomic number of an element refers to the number of:
A. Neutrons
B. Electrons in the outer shell
C. Protons in the nucleus
, 3
D. Total subatomic particles
Correct answer: C
Rationale: The atomic number is the number of protons in the nucleus, which
determines the chemical properties of an element.
4. Which subatomic particle determines the chemical behavior of an atom?
A. Neutron
B. Electron
C. Proton
D. Nucleon
Correct answer: B
Rationale: Electrons, particularly valence electrons, determine how atoms
bond and react with others.
5. An atom has 11 protons, 12 neutrons, and 11 electrons. What is the
atomic mass?
A. 11
B. 12
C. 22
D. 23
Correct answer: D
Rationale: Atomic mass ≈ number of protons + number of neutrons = 11 +
12 = 23.
6. Which of the following best describes isotopes?
A. Atoms with different numbers of electrons
B. Atoms with the same number of protons but different numbers of neutrons
C. Atoms with different numbers of protons
, 4
D. Atoms with different atomic numbers
Correct answer: B
Rationale: Isotopes are forms of the same element (same protons) with
differing neutrons, affecting atomic mass.
7. What is the mass of an electron compared to a proton?
A. Equal
B. 10 times larger
C. 1/10th of a proton
D. Approximately 1/1836th of a proton
Correct answer: D
Rationale: Electrons are significantly lighter than protons and neutrons,
almost negligible in atomic mass.
8. Which part of the atom contains the most mass?
A. Electron cloud
B. Orbitals
C. Nucleus
D. Shells
Correct answer: C
Rationale: The nucleus, composed of protons and neutrons, accounts for
nearly all the atom’s mass.
9. What is the charge of an atom with 9 protons and 10 electrons?
A. +1
B. Neutral
C. –1
D. –2
