HESI A2 CHEMISTRY ACTUAL
EXAM 2026 |150 QUESTIONS
WITH CORRECT ANSWERS AND
RATIONALE, LATEST REVISED
UPDATE,PASSING
GUARRANTEED, GRADED A+
, TABLE OF CONTENTS
1. Atomic Structure (Questions 1-25)
2. Periodic Table and Trends (Questions 26-45)
3. Chemical Bonding (Questions 46-65)
4. Chemical Reactions and Equations (Questions 66-85)
5. Stoichiometry and Mole Concepts (Questions 86-105)
6. Solutions and Concentrations (Questions 106-125)
7. Acids, Bases, and pH (Questions 126-140)
8. Nuclear Chemistry and Biochemistry Basics (Questions 141-150)
SECTION 1: ATOMIC STRUCTURE
Questions 1-25
Question 1
What is the atomic number of an element with 17 protons and 18 neutrons?
A) 17
B) 18
C) 35
D) 1
Correct Answer: A) 17
Rationale: The atomic number equals the number of protons, which is 17. Neutrons
contribute to the mass number (protons + neutrons = 35), not the atomic number. The
atomic number uniquely identifies an element and determines its position on the
periodic table.
,Question 2
Which subatomic particle determines an element's chemical properties?
A) Neutron
B) Proton
C) Electron
D) Nucleus
Correct Answer: C) Electron
Rationale: Electrons, especially valence electrons in the outermost shell, participate in
chemical bonding and reactions, defining chemical properties. Protons determine the
element's identity, and neutrons affect mass and stability. The arrangement of electrons
dictates how atoms interact with one another.
Question 3
An atom with 8 protons, 8 neutrons, and 10 electrons has a charge of:
A) +2
B) -2
C) 0
D) +8
Correct Answer: B) -2
Rationale: Charge is calculated as protons minus electrons (8 - 10 = -2). This atom has
two more electrons than protons, giving it a net negative charge, making it an anion.
Neutrons are neutral and do not affect the overall charge.
Question 4
Which element has the electron configuration 1s²2s²2p⁶3s²3p⁵?
A) Fluorine
B) Chlorine
C) Sulfur
D) Argon
, Correct Answer: B) Chlorine
Rationale: The configuration shows 17 electrons (2+2+6+2+5 = 17), corresponding to
chlorine (atomic number 17). Fluorine has 9 electrons, sulfur has 16, and argon has 18
electrons. The outermost shell (3s²3p⁵) indicates 7 valence electrons, characteristic of
halogens.
Question 5
What makes up the physical structure of an atom?
A) Protons and electrons only
B) A nucleus and electron clouds (orbits)
C) Neutrons and electrons only
D) Protons and neutrons only
Correct Answer: B) A nucleus and electron clouds (orbits)
Rationale: An atom consists of a central nucleus containing protons and neutrons,
surrounded by electrons in regions called electron clouds or orbitals. These orbitals
represent the probability of finding an electron in a particular location around the
nucleus.
Question 6
What composes the center (nucleus) of an atom?
A) Protons and electrons
B) Neutrons and electrons
C) Protons and neutrons
D) Protons, neutrons, and electrons
Correct Answer: C) Protons and neutrons
Rationale: The nucleus contains protons (positively charged) and neutrons (neutral).
Electrons orbit the nucleus in electron clouds and are not part of the nuclear structure.
The nucleus contains over 99.9% of the atom's mass.
EXAM 2026 |150 QUESTIONS
WITH CORRECT ANSWERS AND
RATIONALE, LATEST REVISED
UPDATE,PASSING
GUARRANTEED, GRADED A+
, TABLE OF CONTENTS
1. Atomic Structure (Questions 1-25)
2. Periodic Table and Trends (Questions 26-45)
3. Chemical Bonding (Questions 46-65)
4. Chemical Reactions and Equations (Questions 66-85)
5. Stoichiometry and Mole Concepts (Questions 86-105)
6. Solutions and Concentrations (Questions 106-125)
7. Acids, Bases, and pH (Questions 126-140)
8. Nuclear Chemistry and Biochemistry Basics (Questions 141-150)
SECTION 1: ATOMIC STRUCTURE
Questions 1-25
Question 1
What is the atomic number of an element with 17 protons and 18 neutrons?
A) 17
B) 18
C) 35
D) 1
Correct Answer: A) 17
Rationale: The atomic number equals the number of protons, which is 17. Neutrons
contribute to the mass number (protons + neutrons = 35), not the atomic number. The
atomic number uniquely identifies an element and determines its position on the
periodic table.
,Question 2
Which subatomic particle determines an element's chemical properties?
A) Neutron
B) Proton
C) Electron
D) Nucleus
Correct Answer: C) Electron
Rationale: Electrons, especially valence electrons in the outermost shell, participate in
chemical bonding and reactions, defining chemical properties. Protons determine the
element's identity, and neutrons affect mass and stability. The arrangement of electrons
dictates how atoms interact with one another.
Question 3
An atom with 8 protons, 8 neutrons, and 10 electrons has a charge of:
A) +2
B) -2
C) 0
D) +8
Correct Answer: B) -2
Rationale: Charge is calculated as protons minus electrons (8 - 10 = -2). This atom has
two more electrons than protons, giving it a net negative charge, making it an anion.
Neutrons are neutral and do not affect the overall charge.
Question 4
Which element has the electron configuration 1s²2s²2p⁶3s²3p⁵?
A) Fluorine
B) Chlorine
C) Sulfur
D) Argon
, Correct Answer: B) Chlorine
Rationale: The configuration shows 17 electrons (2+2+6+2+5 = 17), corresponding to
chlorine (atomic number 17). Fluorine has 9 electrons, sulfur has 16, and argon has 18
electrons. The outermost shell (3s²3p⁵) indicates 7 valence electrons, characteristic of
halogens.
Question 5
What makes up the physical structure of an atom?
A) Protons and electrons only
B) A nucleus and electron clouds (orbits)
C) Neutrons and electrons only
D) Protons and neutrons only
Correct Answer: B) A nucleus and electron clouds (orbits)
Rationale: An atom consists of a central nucleus containing protons and neutrons,
surrounded by electrons in regions called electron clouds or orbitals. These orbitals
represent the probability of finding an electron in a particular location around the
nucleus.
Question 6
What composes the center (nucleus) of an atom?
A) Protons and electrons
B) Neutrons and electrons
C) Protons and neutrons
D) Protons, neutrons, and electrons
Correct Answer: C) Protons and neutrons
Rationale: The nucleus contains protons (positively charged) and neutrons (neutral).
Electrons orbit the nucleus in electron clouds and are not part of the nuclear structure.
The nucleus contains over 99.9% of the atom's mass.
