HESI A2 CHEMISTRY TEST 2026/2027 | Questions & Answers
| Updated for Nursing Entrance | Pass Guaranteed - A+
Graded
[Section 1: Matter & Atomic Structure (Q1-10)]
Q1. A nurse observes an IV saline bag after infusion; water evaporates from the inner
walls and dry salt crystals remain. Which statement correctly classifies these
processes?
A. Both are chemical changes because the salt decomposes.
B. Both are physical changes because no new substances form.
C. Evaporation is physical, but salt deposition is chemical.
D. Evaporation is chemical, but salt deposition is physical.
B. Both are physical changes because no new substances form. [CORRECT]
Rationale: Evaporation is a liquid-to-gas phase change and salt deposition is a
dissolved-to-solid phase change; neither process breaks or forms chemical bonds, so
both are physical changes. Distractor A incorrectly assumes decomposition, while C
and D misclassify one process as chemical.
Correct Answer: B
Q2. A magnesium ion, Mg²⁺, has a mass number of 24. How many protons, neutrons,
and electrons does it contain?
A. 12 protons, 12 neutrons, 12 electrons
B. 12 protons, 12 neutrons, 10 electrons
C. 14 protons, 10 neutrons, 12 electrons
D. 24 protons, 12 neutrons, 10 electrons
B. 12 protons, 12 neutrons, 10 electrons. [CORRECT]
,Rationale: Magnesium has atomic number 12, so it always contains 12 protons;
neutrons equal mass number minus atomic number (24 − 12 = 12); the 2+ charge
means it has lost 2 electrons, leaving 10. Distractor A gives the electron count of a
neutral atom, C swaps atomic number and neutron count, and D confuses mass number
with proton count.
Correct Answer: B
Q3. Which pair represents isotopes of the same element?
A. Carbon-12 and Oxygen-16
B. Carbon-12 and Carbon-14
C. Sodium-23 and Magnesium-24
D. Nitrogen-14 and a nitride ion (N³⁻)
B. Carbon-12 and Carbon-14. [CORRECT]
Rationale: Isotopes are atoms of the same element with identical proton counts but
different neutron counts; both carbon isotopes have 6 protons but 6 and 8 neutrons,
respectively. Distractor A compares different elements, C compares different elements
with consecutive atomic numbers, and D compares a neutral atom with an ion of the
same isotope.
Correct Answer: B
Q4. A nitride ion (N³⁻) is formed from a neutral nitrogen atom with mass number 14.
How many protons, neutrons, and electrons are in this ion?
A. 7 protons, 7 neutrons, 7 electrons
B. 7 protons, 7 neutrons, 4 electrons
C. 7 protons, 7 neutrons, 10 electrons
D. 10 protons, 4 neutrons, 7 electrons
C. 7 protons, 7 neutrons, 10 electrons. [CORRECT]
, Rationale: Nitrogen has atomic number 7, giving 7 protons; neutrons equal 14 − 7 = 7;
the 3− charge means the atom gained 3 electrons, resulting in 10 total electrons.
Distractor A describes a neutral nitrogen atom, B subtracts the charge instead of adding
electrons, and D confuses gained electrons with protons.
Correct Answer: C
Q5. How many valence electrons are present in a neutral atom of sulfur (Group 16)?
A. 4
B. 6
C. 8
D. 16
B. 6. [CORRECT]
Rationale: For main-group elements, the number of valence electrons corresponds to
the group number (using the A-group designation); sulfur in Group 16 (VIA) has 6
valence electrons. Distractor A might confuse sulfur with Group 14, C represents a
complete octet rather than valence count, and D is the total electrons in a neutral sulfur
atom.
Correct Answer: B
Q6. Which statement correctly describes the trend in atomic radius across a period
from left to right?
A. Atomic radius increases because more electron shells are added.
B. Atomic radius decreases because nuclear charge increases, pulling electrons closer.
C. Atomic radius remains constant across a period.
D. Atomic radius decreases because the number of neutrons decreases.
B. Atomic radius decreases because nuclear charge increases, pulling electrons closer.
[CORRECT]
| Updated for Nursing Entrance | Pass Guaranteed - A+
Graded
[Section 1: Matter & Atomic Structure (Q1-10)]
Q1. A nurse observes an IV saline bag after infusion; water evaporates from the inner
walls and dry salt crystals remain. Which statement correctly classifies these
processes?
A. Both are chemical changes because the salt decomposes.
B. Both are physical changes because no new substances form.
C. Evaporation is physical, but salt deposition is chemical.
D. Evaporation is chemical, but salt deposition is physical.
B. Both are physical changes because no new substances form. [CORRECT]
Rationale: Evaporation is a liquid-to-gas phase change and salt deposition is a
dissolved-to-solid phase change; neither process breaks or forms chemical bonds, so
both are physical changes. Distractor A incorrectly assumes decomposition, while C
and D misclassify one process as chemical.
Correct Answer: B
Q2. A magnesium ion, Mg²⁺, has a mass number of 24. How many protons, neutrons,
and electrons does it contain?
A. 12 protons, 12 neutrons, 12 electrons
B. 12 protons, 12 neutrons, 10 electrons
C. 14 protons, 10 neutrons, 12 electrons
D. 24 protons, 12 neutrons, 10 electrons
B. 12 protons, 12 neutrons, 10 electrons. [CORRECT]
,Rationale: Magnesium has atomic number 12, so it always contains 12 protons;
neutrons equal mass number minus atomic number (24 − 12 = 12); the 2+ charge
means it has lost 2 electrons, leaving 10. Distractor A gives the electron count of a
neutral atom, C swaps atomic number and neutron count, and D confuses mass number
with proton count.
Correct Answer: B
Q3. Which pair represents isotopes of the same element?
A. Carbon-12 and Oxygen-16
B. Carbon-12 and Carbon-14
C. Sodium-23 and Magnesium-24
D. Nitrogen-14 and a nitride ion (N³⁻)
B. Carbon-12 and Carbon-14. [CORRECT]
Rationale: Isotopes are atoms of the same element with identical proton counts but
different neutron counts; both carbon isotopes have 6 protons but 6 and 8 neutrons,
respectively. Distractor A compares different elements, C compares different elements
with consecutive atomic numbers, and D compares a neutral atom with an ion of the
same isotope.
Correct Answer: B
Q4. A nitride ion (N³⁻) is formed from a neutral nitrogen atom with mass number 14.
How many protons, neutrons, and electrons are in this ion?
A. 7 protons, 7 neutrons, 7 electrons
B. 7 protons, 7 neutrons, 4 electrons
C. 7 protons, 7 neutrons, 10 electrons
D. 10 protons, 4 neutrons, 7 electrons
C. 7 protons, 7 neutrons, 10 electrons. [CORRECT]
, Rationale: Nitrogen has atomic number 7, giving 7 protons; neutrons equal 14 − 7 = 7;
the 3− charge means the atom gained 3 electrons, resulting in 10 total electrons.
Distractor A describes a neutral nitrogen atom, B subtracts the charge instead of adding
electrons, and D confuses gained electrons with protons.
Correct Answer: C
Q5. How many valence electrons are present in a neutral atom of sulfur (Group 16)?
A. 4
B. 6
C. 8
D. 16
B. 6. [CORRECT]
Rationale: For main-group elements, the number of valence electrons corresponds to
the group number (using the A-group designation); sulfur in Group 16 (VIA) has 6
valence electrons. Distractor A might confuse sulfur with Group 14, C represents a
complete octet rather than valence count, and D is the total electrons in a neutral sulfur
atom.
Correct Answer: B
Q6. Which statement correctly describes the trend in atomic radius across a period
from left to right?
A. Atomic radius increases because more electron shells are added.
B. Atomic radius decreases because nuclear charge increases, pulling electrons closer.
C. Atomic radius remains constant across a period.
D. Atomic radius decreases because the number of neutrons decreases.
B. Atomic radius decreases because nuclear charge increases, pulling electrons closer.
[CORRECT]
