,CHEM 121 Module 8 Exam Foundations of General
Chemistry w/Lab | Portage | 26/27 Actual (PDF)
1. Which subatomic particle is found in the nucleus and carries no electrical charge?
A) Proton
B) Electron
C) Neutron
D) Positron
Correct Answer: Neutron
Rationale: The nucleus contains protons (positively charged) and neutrons (neutral). Electrons orbit
the nucleus and are negatively charged, while positrons are antimatter particles not found in stable
nuclei. Options A, B, and D are incorrect because protons are charged, electrons are outside the
nucleus, and positrons are not nuclear components.
2. What is the atomic number (Z) of an element defined as?
A) The number of neutrons in the nucleus
B) The number of protons in the nucleus
C) The sum of protons and neutrons
D) The number of electrons in the outermost shell
Correct Answer: The number of protons in the nucleus
Rationale: The atomic number (Z) is the number of protons in the nucleus and defines the identity of
an element. The mass number (A) is the sum of protons and neutrons. Options A, C, and D describe
other atomic properties that do not define the element's identity.
3. Which of the following best defines isotopes?
,A) Atoms of the same element with different numbers of protons
B) Atoms of the same element with different numbers of neutrons
C) Atoms of different elements with the same mass number
D) Atoms that have gained or lost electrons
Correct Answer: Atoms of the same element with different numbers of neutrons
Rationale: Isotopes are atoms of the same element (same atomic number) that differ in the number of
neutrons, resulting in different mass numbers. Options A, C, and D describe different atomic species or
concepts that do not correctly define isotopes.
4. What is the mass number (A) of an atom with 17 protons and 20 neutrons?
A) 17
B) 20
C) 37
D) 3
Correct Answer: 37
Rationale: Mass number (A) = protons + neutrons = 17 + 20 = 37. Option A is the atomic number,
option B is the number of neutrons, and option D is the difference. Options A, B, and D are incorrect.
5. Which force holds the nucleus together by acting between protons and neutrons?
A) Electrostatic force
B) Gravitational force
C) Strong nuclear force
D) Weak nuclear force
, Correct Answer: Strong nuclear force
Rationale: The strong nuclear force is the attractive force that binds protons and neutrons together in
the nucleus, overcoming the electrostatic repulsion between protons. Options A, B, and D are
incorrect because electrostatic force repels protons, gravitational force is negligible, and weak nuclear
force is involved in radioactive decay.
6. The band of stability is a plot of which two quantities?
A) Atomic number versus mass number
B) Number of neutrons versus number of protons
C) Number of electrons versus number of protons
D) Mass defect versus binding energy
Correct Answer: Number of neutrons versus number of protons
Rationale: The band of stability is a plot of the number of neutrons (N) versus the number of protons
(Z) for stable nuclei, showing the N/Z ratio required for stability. Options A, C, and D do not represent
the axes of this plot.
7. What is the mass defect of a nucleus?
A) The mass of the electrons in an atom
B) The difference between the calculated mass and the measured mass of a nucleus
C) The mass of the protons in a nucleus
D) The energy released during a chemical reaction
Correct Answer: The difference between the calculated mass and the measured mass of a nucleus
Chemistry w/Lab | Portage | 26/27 Actual (PDF)
1. Which subatomic particle is found in the nucleus and carries no electrical charge?
A) Proton
B) Electron
C) Neutron
D) Positron
Correct Answer: Neutron
Rationale: The nucleus contains protons (positively charged) and neutrons (neutral). Electrons orbit
the nucleus and are negatively charged, while positrons are antimatter particles not found in stable
nuclei. Options A, B, and D are incorrect because protons are charged, electrons are outside the
nucleus, and positrons are not nuclear components.
2. What is the atomic number (Z) of an element defined as?
A) The number of neutrons in the nucleus
B) The number of protons in the nucleus
C) The sum of protons and neutrons
D) The number of electrons in the outermost shell
Correct Answer: The number of protons in the nucleus
Rationale: The atomic number (Z) is the number of protons in the nucleus and defines the identity of
an element. The mass number (A) is the sum of protons and neutrons. Options A, C, and D describe
other atomic properties that do not define the element's identity.
3. Which of the following best defines isotopes?
,A) Atoms of the same element with different numbers of protons
B) Atoms of the same element with different numbers of neutrons
C) Atoms of different elements with the same mass number
D) Atoms that have gained or lost electrons
Correct Answer: Atoms of the same element with different numbers of neutrons
Rationale: Isotopes are atoms of the same element (same atomic number) that differ in the number of
neutrons, resulting in different mass numbers. Options A, C, and D describe different atomic species or
concepts that do not correctly define isotopes.
4. What is the mass number (A) of an atom with 17 protons and 20 neutrons?
A) 17
B) 20
C) 37
D) 3
Correct Answer: 37
Rationale: Mass number (A) = protons + neutrons = 17 + 20 = 37. Option A is the atomic number,
option B is the number of neutrons, and option D is the difference. Options A, B, and D are incorrect.
5. Which force holds the nucleus together by acting between protons and neutrons?
A) Electrostatic force
B) Gravitational force
C) Strong nuclear force
D) Weak nuclear force
, Correct Answer: Strong nuclear force
Rationale: The strong nuclear force is the attractive force that binds protons and neutrons together in
the nucleus, overcoming the electrostatic repulsion between protons. Options A, B, and D are
incorrect because electrostatic force repels protons, gravitational force is negligible, and weak nuclear
force is involved in radioactive decay.
6. The band of stability is a plot of which two quantities?
A) Atomic number versus mass number
B) Number of neutrons versus number of protons
C) Number of electrons versus number of protons
D) Mass defect versus binding energy
Correct Answer: Number of neutrons versus number of protons
Rationale: The band of stability is a plot of the number of neutrons (N) versus the number of protons
(Z) for stable nuclei, showing the N/Z ratio required for stability. Options A, C, and D do not represent
the axes of this plot.
7. What is the mass defect of a nucleus?
A) The mass of the electrons in an atom
B) The difference between the calculated mass and the measured mass of a nucleus
C) The mass of the protons in a nucleus
D) The energy released during a chemical reaction
Correct Answer: The difference between the calculated mass and the measured mass of a nucleus
