CHEM 103 Module 2 Exam: Atomic Structure, Periodic Table, and
Electron Configuration 2026/2027 UPDATE
1. Which subatomic particle has a relative charge of -1 and is found outside the
nucleus?
A. Electron
B. Neutron
C. Proton
D. Positron
Answer: A
Rationale: Electrons are negatively charged particles that orbit the nucleus in specific
energy levels or orbitals.
2. The atomic number of an element is always equal to the number of:
A. Neutrons
B. Electrons in an ion
C. Protons
D. Protons plus neutrons
Answer: C
Rationale: The atomic number uniquely identifies an element and represents the number
of protons in the nucleus.
,3. Isotopes of the same element have the same number of protons but different
numbers of:
A. Electrons
B. Neutrons
C. Orbitals
D. Valence shells
Answer: B
Rationale: Isotopes are atoms of the same element with different mass numbers due to a
varying number of neutrons.
4. The mass number of an atom is defined as the sum of:
A. Protons and electrons
B. Atomic number and charge
C. Neutrons and electrons
D. Protons and neutrons
Answer: D
Rationale: Mass number (A) is the total count of nucleons (protons and neutrons) in the
nucleus.
5. Which scientist is credited with the ‘Plum Pudding’ model of the atom?
A. Ernest Rutherford
B. John Dalton
C. J.J. Thomson
D. Niels Bohr
Answer: C
Rationale: J.J. Thomson proposed the plum pudding model after discovering the electron,
suggesting negative charges were embedded in a positive sphere.
, 6. The gold foil experiment conducted by Rutherford led to the discovery of:
A. The electron
B. The neutron
C. The nucleus
D. Quarks
Answer: C
Rationale: Rutherford’s experiment showed that most alpha particles passed through gold
foil, but some deflected, suggesting a small, dense, positive nucleus.
7. What is the maximum number of electrons that can occupy the first (n=1)
energy level?
A. 18
B. 8
C. 2
D. 32
Answer: C
Rationale: The first energy level only contains the 1s orbital, which can hold a maximum of
2 electrons.
8. The vertical columns in the periodic table are known as:
A. Periods
B. Series
C. Blocks
D. Groups
Answer: D
Rationale: Groups or families are the vertical columns; elements within a group share
similar chemical properties.
Electron Configuration 2026/2027 UPDATE
1. Which subatomic particle has a relative charge of -1 and is found outside the
nucleus?
A. Electron
B. Neutron
C. Proton
D. Positron
Answer: A
Rationale: Electrons are negatively charged particles that orbit the nucleus in specific
energy levels or orbitals.
2. The atomic number of an element is always equal to the number of:
A. Neutrons
B. Electrons in an ion
C. Protons
D. Protons plus neutrons
Answer: C
Rationale: The atomic number uniquely identifies an element and represents the number
of protons in the nucleus.
,3. Isotopes of the same element have the same number of protons but different
numbers of:
A. Electrons
B. Neutrons
C. Orbitals
D. Valence shells
Answer: B
Rationale: Isotopes are atoms of the same element with different mass numbers due to a
varying number of neutrons.
4. The mass number of an atom is defined as the sum of:
A. Protons and electrons
B. Atomic number and charge
C. Neutrons and electrons
D. Protons and neutrons
Answer: D
Rationale: Mass number (A) is the total count of nucleons (protons and neutrons) in the
nucleus.
5. Which scientist is credited with the ‘Plum Pudding’ model of the atom?
A. Ernest Rutherford
B. John Dalton
C. J.J. Thomson
D. Niels Bohr
Answer: C
Rationale: J.J. Thomson proposed the plum pudding model after discovering the electron,
suggesting negative charges were embedded in a positive sphere.
, 6. The gold foil experiment conducted by Rutherford led to the discovery of:
A. The electron
B. The neutron
C. The nucleus
D. Quarks
Answer: C
Rationale: Rutherford’s experiment showed that most alpha particles passed through gold
foil, but some deflected, suggesting a small, dense, positive nucleus.
7. What is the maximum number of electrons that can occupy the first (n=1)
energy level?
A. 18
B. 8
C. 2
D. 32
Answer: C
Rationale: The first energy level only contains the 1s orbital, which can hold a maximum of
2 electrons.
8. The vertical columns in the periodic table are known as:
A. Periods
B. Series
C. Blocks
D. Groups
Answer: D
Rationale: Groups or families are the vertical columns; elements within a group share
similar chemical properties.
