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Exam Review

Key Facts: HESI A2 Chemistry Exam

~25

Questions on Chemistry subsection

Elsevier handbook

25 min

Section time limit

Elsevier handbook

100

Free practice questions here

OpenExamPrep

Elsevier's HESI A2 Chemistry section presents about 25 multiple-choice items in 25 minutes, with heavy weighting on atomic structure, bonding, reaction types, and acid-base chemistry for nursing-school applicants in 2026.

Sample HESI A2 Chemistry Practice Questions

Try these sample questions to review concepts for the HESI A2 Chemistry exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1What subatomic particle has a positive electrical charge and is located in the nucleus of an atom?
A.Electron
B.Neutron
C.Proton
D.Photon
Explanation: Protons are positively charged subatomic particles found in the nucleus of an atom. The number of protons defines the element's atomic number and identity (e.g., all carbon atoms have 6 protons). Neutrons share the nucleus but carry no charge, while electrons are negatively charged particles that orbit the nucleus in electron shells.
2What does the atomic number of an element represent?
A.The number of neutrons in the nucleus
B.The number of protons in the nucleus
C.The total number of protons plus neutrons
D.The number of electron shells
Explanation: The atomic number equals the number of protons in the nucleus of an atom and uniquely identifies the element. For example, every atom with 6 protons is carbon, and every atom with 8 protons is oxygen. In a neutral atom, the atomic number also equals the number of electrons.
3Two atoms are isotopes of each other if they have the same number of ____ but different numbers of ____.
A.protons; neutrons
B.neutrons; protons
C.electrons; protons
D.protons; electrons
Explanation: Isotopes are atoms of the same element that have the same number of protons (same atomic number) but different numbers of neutrons. For example, carbon-12 and carbon-14 both have 6 protons, but carbon-12 has 6 neutrons while carbon-14 has 8. Isotopes share chemical properties but differ in mass and nuclear stability.
4How many electrons can the second electron shell (n=2) hold at maximum?
A.2
B.8
C.18
D.32
Explanation: The maximum number of electrons that any shell can hold is given by the formula 2n^2, where n is the principal quantum number. For n=2, the maximum is 2(2)^2 = 8 electrons. This explains the octet rule, since most main-group atoms become stable with 8 electrons in their outer shell.
5An atom of sodium (Na) has an atomic number of 11 and a mass number of 23. How many neutrons does this atom contain?
A.11
B.12
C.23
D.34
Explanation: The number of neutrons is calculated by subtracting the atomic number (protons) from the mass number (protons + neutrons): 23 - 11 = 12 neutrons. Sodium-23 is the most abundant naturally occurring isotope of sodium, accounting for essentially all natural sodium.
6Which of the following is the correct electron configuration for a neutral oxygen atom (atomic number 8)?
A.1s^2 2s^2 2p^2
B.1s^2 2s^2 2p^4
C.1s^2 2s^2 2p^6
D.1s^2 2s^4 2p^2
Explanation: Oxygen has 8 electrons distributed as 1s^2 2s^2 2p^4: two electrons fill the 1s subshell, two fill the 2s subshell, and four occupy the 2p subshell. The unfilled 2p subshell (which can hold 6 electrons) makes oxygen highly reactive — it tends to gain 2 electrons to complete its octet.
7Which group on the periodic table contains the noble gases?
A.Group 1
B.Group 2
C.Group 17
D.Group 18
Explanation: The noble gases occupy Group 18 (formerly called Group 0 or VIIIA) on the far right of the periodic table. They include helium, neon, argon, krypton, xenon, and radon. Their outermost electron shells are completely filled, which makes them chemically inert and largely unreactive under normal conditions.
8What is the term for the horizontal rows of the periodic table?
A.Groups
B.Periods
C.Families
D.Series
Explanation: Horizontal rows on the periodic table are called periods. Each period corresponds to the principal quantum number (n) of the outermost electron shell being filled. There are 7 periods on the modern periodic table, and elements within the same period show trends in properties as atomic number increases left to right.
9Which element has the highest electronegativity?
A.Hydrogen
B.Oxygen
C.Fluorine
D.Chlorine
Explanation: Fluorine has the highest electronegativity of any element on the Pauling scale (3.98). Electronegativity increases moving up and to the right on the periodic table, and fluorine sits at the top right (excluding the noble gases). This strong attraction for electrons makes fluorine an extremely reactive nonmetal.
10As you move down a group on the periodic table, the atomic radius of the elements generally:
A.Decreases
B.Increases
C.Remains constant
D.Fluctuates randomly
Explanation: Atomic radius increases as you move down a group because each successive element has one more occupied electron shell. The additional shells place the outermost electrons farther from the nucleus. Although nuclear charge also increases, the added inner shells shield the outer electrons, so the overall size grows.

About the HESI A2 Chemistry Exam

The HESI A2 Chemistry subsection assesses foundational chemistry: atomic structure, bonding, reactions, acids/bases, and solutions. It is required by many but not all nursing programs.

Exam sponsor: Elsevier / nursing school testing centers. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Questions

25 questions

Time Limit

25 minutes

Passing Score

School set (75-80%+)

Exam / Certification Fees

Bundled in HESI A2 registration

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Official sources

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

High

Atomic Structure

Subatomic particles, isotopes, periodic-table trends

High

Chemical Bonding

Ionic vs covalent, polarity, intermolecular forces

High

Chemical Reactions

Reaction types and balancing equations

High

Acids & Bases

pH scale, strong vs weak, buffers

Medium

Solutions

Concentration, molarity, dilution, electrolytes

Medium

Gas Laws

Boyle's, Charles's, ideal-gas relationships

Preparing for the HESI A2 Chemistry Exam

What You Need to Know

  • Passing score: School set (75-80%+)
  • Exam length: 25 questions
  • Time limit: 25 minutes
  • Exam / certification fees: Bundled in HESI A2 registration Official sources

Using Our Practice Resources

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

HESI A2 Chemistry: Suggested Study Strategy

1Memorize the polyatomic ions and common monatomic charges
2Practice balancing chemical equations daily
3Master pH calculations and acid-base relationships
4Use the periodic table to predict bonding behavior

Frequently Asked Questions

Do I need to take HESI A2 Chemistry?

Programs choose which sections are required. Some BSN programs require Chemistry; many ADN programs do not. Check with your specific program.

What's the hardest part of HESI Chemistry?

Stoichiometry, reaction balancing, and acid-base chemistry are typically the highest-difficulty areas.