CEM 141 EXAM 3 MSU NEWEST 2026 ACTUAL EXAM
TEST BANK| MSU CEM 141 EXAM 3 REVIEW WITH 350
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 charge of +1?
A) Electron
B) Neutron
C) Proton
D) Positron
Answer: C
Rationale: Protons have mass ≈1 amu and charge +1. Neutrons
have mass ≈1 amu but charge 0. Electrons have negligible mass.
2. An atom contains 15 protons, 16 neutrons, and 15
electrons. What is its mass number?
A) 15
B) 16
C) 31
D) 46
1
,Answer: C
Rationale: Mass number = protons + neutrons = 15 + 16 = 31.
Atomic number = protons = 15 (phosphorus).
3. Which statement about isotopes is correct?
A) Same number of protons, different number of electrons
B) Same number of protons, different number of neutrons
C) Same number of neutrons, different number of protons
D) Same mass number, different atomic numbers
Answer: B
Rationale: Isotopes have identical atomic numbers (same
element) but different mass numbers (different neutron counts).
4. How many electrons can occupy an orbital with quantum
numbers n=3, l=2?
A) 1
B) 2
C) 6
D) 10
2
,Answer: B
Rationale: Any single orbital holds a maximum of 2 electrons
(Pauli exclusion principle). n=3, l=2 is a 3d orbital (there are 5 d
orbitals total).
5. Which element has the electron configuration [Ar] 4s² 3d¹⁰
4p²?
A) Zn
B) Ge
C) Sn
D) Pb
Answer: B
Rationale: [Ar] = 18 electrons + 12 (4s² 3d¹⁰ 4p²) = 30 total
→ zinc? Wait — that sums to 30 electrons (Zn), but Zn is
[Ar]4s²3d¹⁰ (not 4p²). Let me recalc: [Ar] = 18. Add 4s²=2 (20),
3d¹⁰=10 (30), 4p²=2 (32). Atomic number 32 = Germanium
(Ge). Yes, correct.
6. The atomic number of an element is 26. How many
electrons does Fe³⁺ have?
3
, A) 23
B) 26
C) 29
D) 56
Answer: A
Rationale: Neutral Fe has 26 electrons. Fe³⁺ lost 3 electrons →
26 − 3 = 23 electrons.
7. Which element is a metal?
A) Carbon
B) Sulfur
C) Sodium
D) Chlorine
Answer: C
Rationale: Sodium (Group 1) is an alkali metal. C, S, Cl are
nonmetals.
8. Which combination represents an atom with 20 protons, 20
neutrons, and 18 electrons?
A) Ca²⁺
4
TEST BANK| MSU CEM 141 EXAM 3 REVIEW WITH 350
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 charge of +1?
A) Electron
B) Neutron
C) Proton
D) Positron
Answer: C
Rationale: Protons have mass ≈1 amu and charge +1. Neutrons
have mass ≈1 amu but charge 0. Electrons have negligible mass.
2. An atom contains 15 protons, 16 neutrons, and 15
electrons. What is its mass number?
A) 15
B) 16
C) 31
D) 46
1
,Answer: C
Rationale: Mass number = protons + neutrons = 15 + 16 = 31.
Atomic number = protons = 15 (phosphorus).
3. Which statement about isotopes is correct?
A) Same number of protons, different number of electrons
B) Same number of protons, different number of neutrons
C) Same number of neutrons, different number of protons
D) Same mass number, different atomic numbers
Answer: B
Rationale: Isotopes have identical atomic numbers (same
element) but different mass numbers (different neutron counts).
4. How many electrons can occupy an orbital with quantum
numbers n=3, l=2?
A) 1
B) 2
C) 6
D) 10
2
,Answer: B
Rationale: Any single orbital holds a maximum of 2 electrons
(Pauli exclusion principle). n=3, l=2 is a 3d orbital (there are 5 d
orbitals total).
5. Which element has the electron configuration [Ar] 4s² 3d¹⁰
4p²?
A) Zn
B) Ge
C) Sn
D) Pb
Answer: B
Rationale: [Ar] = 18 electrons + 12 (4s² 3d¹⁰ 4p²) = 30 total
→ zinc? Wait — that sums to 30 electrons (Zn), but Zn is
[Ar]4s²3d¹⁰ (not 4p²). Let me recalc: [Ar] = 18. Add 4s²=2 (20),
3d¹⁰=10 (30), 4p²=2 (32). Atomic number 32 = Germanium
(Ge). Yes, correct.
6. The atomic number of an element is 26. How many
electrons does Fe³⁺ have?
3
, A) 23
B) 26
C) 29
D) 56
Answer: A
Rationale: Neutral Fe has 26 electrons. Fe³⁺ lost 3 electrons →
26 − 3 = 23 electrons.
7. Which element is a metal?
A) Carbon
B) Sulfur
C) Sodium
D) Chlorine
Answer: C
Rationale: Sodium (Group 1) is an alkali metal. C, S, Cl are
nonmetals.
8. Which combination represents an atom with 20 protons, 20
neutrons, and 18 electrons?
A) Ca²⁺
4
