CHEM 121 Module 2 Practice Exam – 2 Versions with Answers & Rationales

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CHEM 121 – Module 2 Practice Exam 2 VERSIONS

Atomic Structure & Periodic Table

1. Which subatomic particle has a positive charge?
A. Electron
B. Neutron
C. Proton
D. Positron
Answer: C



2. The atomic number of an element represents the number of:
A. Neutrons
B. Protons
C. Electrons + neutrons
D. Isotopes
Answer: B



3. Which particle has the least mass?
A. Proton
B. Neutron
C. Electron
D. Nucleus
Answer: C



4. Isotopes of an element differ in the number of:
A. Protons
B. Electrons
C. Neutrons
D. Charges
Answer: C




2026 2027 GRADED A+

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5. An atom with 17 protons and 18 electrons has a charge of:
A. +1
B. 0
C. −1
D. +17
Answer: C



6. Which element has atomic number 12?
A. Na
B. Mg
C. Al
D. Ca
Answer: B



7. The mass number equals:
A. Protons only
B. Neutrons only
C. Protons + neutrons
D. Protons − electrons
Answer: C



8. Which element is a halogen?
A. Oxygen
B. Nitrogen
C. Chlorine
D. Neon
Answer: C



9. Elements in the same group have the same number of:
A. Neutrons
B. Protons
C. Valence electrons
D. Atomic mass
Answer: C




2026 2027 GRADED A+

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10. Atomic radius generally increases:
A. Left to right across a period
B. Top to bottom down a group
C. As electronegativity increases
D. As ionization energy increases
Answer: B



Ions & Charges

11. A cation is formed when an atom:
A. Gains electrons
B. Loses electrons
C. Gains neutrons
D. Loses neutrons
Answer: B



12. Which ion has a +2 charge?
A. Na⁺
B. Ca²⁺
C. Cl⁻
D. O²⁻
Answer: B



13. Which element commonly forms a −1 ion?
A. Sodium
B. Magnesium
C. Chlorine
D. Aluminum
Answer: C



14. The charge on an ion depends on:
A. Protons only
B. Neutrons only
C. Protons and electrons
D. Mass number
Answer: C




2026 2027 GRADED A+