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CHEMISTRY PLACEMENT (ALEKS) 2026
PRACTICE EXAM COMPLETE (70) CURRENT
TESTING QUESTIONS AND CORRECT
ANSWERS WITH DETAILED
RATIONALES|GRADED A+.
CHEMISTRY
Below is a Chemistry Placement Practice Exam in the style of ALEKS, with
70 questions covering typical topics: atomic structure, periodic trends,
bonding, stoichiometry, reactions, thermochemistry, gases, solutions,
kinetics, equilibrium, acids/bases, and basic organic chemistry. Each
question includes four answer choices (A–D), the correct answer, and a
brief explanation.
MULTIPLE CHOICE.
ALEKS Chemistry Placement – Practice Exam
1. Which subatomic particle has a positive charge?
A) Electron
B) Neutron
C) Proton
D) Positron
Answer: C. Proton
Explanation: Protons have a positive charge. Electrons are negative;
neutrons are neutral.
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2. The atomic number of an element is defined as the number of:
A) Neutrons
B) Protons
C) Electrons in the outermost shell
D) Protons plus neutrons
Answer: B. Protons
Explanation: Atomic number = number of protons. It determines
the element's identity.
3. How many protons, neutrons, and electrons are in an atom of
⁴⁰₂₀Ca?
A) 20 protons, 20 neutrons, 20 electrons
B) 20 protons, 20 neutrons, 18 electrons
C) 20 protons, 40 neutrons, 20 electrons
D) 40 protons, 20 neutrons, 40 electrons
Answer: A. 20 protons, 20 neutrons, 20 electrons
Explanation: The subscript 20 is the atomic number (protons). The
mass number 40 minus 20 = 20 neutrons. Neutral atom has 20
electrons.
4. Which of the following represents a pair of isotopes?
A) ¹⁴C and ¹⁴N
B) ³²S and ³²S²⁻
C) ³⁵Cl and ³⁷Cl
D) H₂O and D₂O
Answer: C. ³⁵Cl and ³⁷Cl
Explanation: Isotopes are atoms of the same element (same
protons) with different numbers of neutrons.
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5. Which element is a noble gas?
A) Oxygen
B) Chlorine
C) Argon
D) Nitrogen
Answer: C. Argon
Explanation: Noble gases are Group 18: He, Ne, Ar, Kr, Xe, Rn.
6. Which group of the periodic table contains alkali metals?
A) Group 1
B) Group 2
C) Group 17
D) Group 18
Answer: A. Group 1 (excluding hydrogen)
Explanation: Alkali metals are Li, Na, K, Rb, Cs, Fr.
7. Which element has the largest atomic radius?
A) Fluorine
B) Chlorine
C) Bromine
D) Iodine
Answer: D. Iodine
Explanation: Atomic radius increases down a group.
8. Which element has the highest electronegativity?
A) Fluorine
B) Chlorine
C) Oxygen
D) Nitrogen
CHEMISTRY PLACEMENT (ALEKS) 2026
PRACTICE EXAM COMPLETE (70) CURRENT
TESTING QUESTIONS AND CORRECT
ANSWERS WITH DETAILED
RATIONALES|GRADED A+.
CHEMISTRY
Below is a Chemistry Placement Practice Exam in the style of ALEKS, with
70 questions covering typical topics: atomic structure, periodic trends,
bonding, stoichiometry, reactions, thermochemistry, gases, solutions,
kinetics, equilibrium, acids/bases, and basic organic chemistry. Each
question includes four answer choices (A–D), the correct answer, and a
brief explanation.
MULTIPLE CHOICE.
ALEKS Chemistry Placement – Practice Exam
1. Which subatomic particle has a positive charge?
A) Electron
B) Neutron
C) Proton
D) Positron
Answer: C. Proton
Explanation: Protons have a positive charge. Electrons are negative;
neutrons are neutral.
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2. The atomic number of an element is defined as the number of:
A) Neutrons
B) Protons
C) Electrons in the outermost shell
D) Protons plus neutrons
Answer: B. Protons
Explanation: Atomic number = number of protons. It determines
the element's identity.
3. How many protons, neutrons, and electrons are in an atom of
⁴⁰₂₀Ca?
A) 20 protons, 20 neutrons, 20 electrons
B) 20 protons, 20 neutrons, 18 electrons
C) 20 protons, 40 neutrons, 20 electrons
D) 40 protons, 20 neutrons, 40 electrons
Answer: A. 20 protons, 20 neutrons, 20 electrons
Explanation: The subscript 20 is the atomic number (protons). The
mass number 40 minus 20 = 20 neutrons. Neutral atom has 20
electrons.
4. Which of the following represents a pair of isotopes?
A) ¹⁴C and ¹⁴N
B) ³²S and ³²S²⁻
C) ³⁵Cl and ³⁷Cl
D) H₂O and D₂O
Answer: C. ³⁵Cl and ³⁷Cl
Explanation: Isotopes are atoms of the same element (same
protons) with different numbers of neutrons.
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5. Which element is a noble gas?
A) Oxygen
B) Chlorine
C) Argon
D) Nitrogen
Answer: C. Argon
Explanation: Noble gases are Group 18: He, Ne, Ar, Kr, Xe, Rn.
6. Which group of the periodic table contains alkali metals?
A) Group 1
B) Group 2
C) Group 17
D) Group 18
Answer: A. Group 1 (excluding hydrogen)
Explanation: Alkali metals are Li, Na, K, Rb, Cs, Fr.
7. Which element has the largest atomic radius?
A) Fluorine
B) Chlorine
C) Bromine
D) Iodine
Answer: D. Iodine
Explanation: Atomic radius increases down a group.
8. Which element has the highest electronegativity?
A) Fluorine
B) Chlorine
C) Oxygen
D) Nitrogen
