CEM 141 EXAM 1 MSU NEWEST 2026 ACTUAL EXAM
TEST BANK| MSU CEM 141 EXAM 1 REVIEW WITH 300
REAL EXAM QUESTIONS AND CORRECT VERIFIED
ANSWERS/ ALREADY GRADED A+ (MOST RECENT!!)
1. Which subatomic particle has a relative mass of
approximately 1 amu and a positive charge?
A) Electron
B) Neutron
C) Proton
D) Positron
Correct Answer: C
Rationale: Protons have a mass of ~1 amu and a charge of +1;
neutrons are neutral; electrons are much lighter.
2. According to Coulomb’s law, if the distance between two
charges is tripled, the electrostatic force becomes:
A) 3 times larger
B) 9 times larger
C) 1/3 as large
D) 1/9 as large
Correct Answer: D
1
,Rationale: F ∝ 1/r²; tripling r (×3) makes force 1/3² = 1/9 of
original.
3. Which experiment led to the discovery of the electron?
A) Gold foil experiment
B) Cathode ray tube experiment
C) Oil drop experiment
D) Alpha scattering experiment
Correct Answer: B
Rationale: J.J. Thomson used cathode ray tubes to discover
electrons and measure their charge-to-mass ratio.
4. In Rutherford’s gold foil experiment, most alpha particles
passed straight through. This indicated that:
A) The atom is mostly empty space
B) The nucleus is positively charged
C) Electrons orbit in fixed paths
D) The atom has a uniform positive charge
Correct Answer: A
Rationale: Most alpha particles passed through undeflected
because atoms are mostly empty space; a few deflected due to
a small, dense nucleus.
2
,5. Which statement about isotopes is correct?
A) Isotopes have the same number of protons but different
numbers of neutrons
B) Isotopes have the same number of neutrons but different
numbers of protons
C) Isotopes have the same mass number
D) Isotopes have the same atomic mass
Correct Answer: A
Rationale: Isotopes of an element have identical atomic number
(protons) but vary in neutron number.
6. The atomic number of an element is defined as the number
of:
A) Neutrons
B) Protons
C) Electrons in a neutral atom
D) Both B and C
Correct Answer: D
Rationale: Atomic number = number of protons; in a neutral
atom, number of electrons equals number of protons.
7. Which particle has the smallest mass?
A) Proton
3
, B) Neutron
C) Electron
D) Alpha particle
Correct Answer: C
Rationale: Electron mass ≈ 9.11 × 10⁻³¹ kg; proton/neutron ≈
1.67 × 10⁻²⁷ kg (about 1836 times heavier).
8. How many neutrons are in an atom of carbon-14 (¹⁴C)?
A) 6
B) 8
C) 14
D) 20
Correct Answer: B
Rationale: Mass number = protons + neutrons; carbon has 6
protons; 14 - 6 = 8 neutrons.
9. Which scientist proposed the planetary model of the atom
with electrons orbiting the nucleus?
A) Dalton
B) Thomson
C) Rutherford
D) Bohr
Correct Answer: C
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TEST BANK| MSU CEM 141 EXAM 1 REVIEW WITH 300
REAL EXAM QUESTIONS AND CORRECT VERIFIED
ANSWERS/ ALREADY GRADED A+ (MOST RECENT!!)
1. Which subatomic particle has a relative mass of
approximately 1 amu and a positive charge?
A) Electron
B) Neutron
C) Proton
D) Positron
Correct Answer: C
Rationale: Protons have a mass of ~1 amu and a charge of +1;
neutrons are neutral; electrons are much lighter.
2. According to Coulomb’s law, if the distance between two
charges is tripled, the electrostatic force becomes:
A) 3 times larger
B) 9 times larger
C) 1/3 as large
D) 1/9 as large
Correct Answer: D
1
,Rationale: F ∝ 1/r²; tripling r (×3) makes force 1/3² = 1/9 of
original.
3. Which experiment led to the discovery of the electron?
A) Gold foil experiment
B) Cathode ray tube experiment
C) Oil drop experiment
D) Alpha scattering experiment
Correct Answer: B
Rationale: J.J. Thomson used cathode ray tubes to discover
electrons and measure their charge-to-mass ratio.
4. In Rutherford’s gold foil experiment, most alpha particles
passed straight through. This indicated that:
A) The atom is mostly empty space
B) The nucleus is positively charged
C) Electrons orbit in fixed paths
D) The atom has a uniform positive charge
Correct Answer: A
Rationale: Most alpha particles passed through undeflected
because atoms are mostly empty space; a few deflected due to
a small, dense nucleus.
2
,5. Which statement about isotopes is correct?
A) Isotopes have the same number of protons but different
numbers of neutrons
B) Isotopes have the same number of neutrons but different
numbers of protons
C) Isotopes have the same mass number
D) Isotopes have the same atomic mass
Correct Answer: A
Rationale: Isotopes of an element have identical atomic number
(protons) but vary in neutron number.
6. The atomic number of an element is defined as the number
of:
A) Neutrons
B) Protons
C) Electrons in a neutral atom
D) Both B and C
Correct Answer: D
Rationale: Atomic number = number of protons; in a neutral
atom, number of electrons equals number of protons.
7. Which particle has the smallest mass?
A) Proton
3
, B) Neutron
C) Electron
D) Alpha particle
Correct Answer: C
Rationale: Electron mass ≈ 9.11 × 10⁻³¹ kg; proton/neutron ≈
1.67 × 10⁻²⁷ kg (about 1836 times heavier).
8. How many neutrons are in an atom of carbon-14 (¹⁴C)?
A) 6
B) 8
C) 14
D) 20
Correct Answer: B
Rationale: Mass number = protons + neutrons; carbon has 6
protons; 14 - 6 = 8 neutrons.
9. Which scientist proposed the planetary model of the atom
with electrons orbiting the nucleus?
A) Dalton
B) Thomson
C) Rutherford
D) Bohr
Correct Answer: C
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