,CHEM 103 Module 2 Exam | General
Chemistry I w/Lab | Portage Learning | Q & A
| 2026 Edition
1. An atom or molecule that contains unequal numbers of protons and electrons is called a(n):
A) Isotope
B) Ion
C) Isomer
D) Nuclide
Correct Answer: Ion
Rationale: An ion is defined as an atom or molecule that has a net electrical charge because the total
number of electrons is not equal to the total number of protons. Isotopes have the same number of
protons but different neutrons, while isomers have the same formula but different structures.
2. Which subatomic particle has a relative mass of approximately 1 amu and a charge of 0?
A) Proton
B) Electron
C) Neutron
D) Positron
Correct Answer: Neutron
Rationale: A neutron has a mass of approximately 1 atomic mass unit (amu) and is electrically neutral
(charge of 0). Protons also have a mass of about 1 amu but carry a +1 charge, while electrons have
negligible mass and a -1 charge.
3. The modern periodic law states that the properties of elements are a periodic function of their:
A) Atomic mass
,B) Atomic number
C) Number of neutrons
D) Mass number
Correct Answer: Atomic number
Rationale: The modern periodic law states that the physical and chemical properties of elements are
periodic functions of their atomic numbers. Mendeleev's original table was based on atomic mass, but
Moseley's work established atomic number as the fundamental organizing principle.
4. Across a period from left to right, the atomic radius generally:
A) Increases
B) Decreases
C) Remains constant
D) Varies unpredictably
Correct Answer: Decreases
Rationale: Moving left to right across a period, protons are added to the nucleus, increasing the nuclear
charge. Electrons are added to the same principal energy level, so shielding remains relatively constant.
The increased effective nuclear charge pulls the electron cloud inward, decreasing atomic radius.
5. Which element has the largest atomic radius among the halogens?
A) Fluorine (F)
B) Chlorine (Cl)
C) Bromine (Br)
D) Iodine (I)
Correct Answer: Iodine (I)
, Rationale: Atomic radius increases as you move down a group because additional electron shells are
added. Among the halogens, iodine is at the bottom of Group 17 and therefore has the largest atomic
radius.
6. Show the calculation of the molecular weight for (NH₄)₂CrO₄, reporting your answer to 2 places after
the decimal.
A) 152.08 g/mol
B) 150.00 g/mol
C) 154.12 g/mol
D) 149.08 g/mol
Correct Answer: 152.08 g/mol
Rationale: The calculation is: 2N (2 × 14.01 = 28.02) + 8H (8 × 1.008 = 8.064) + Cr (52.00) + 4O (4 × 16.00
= 64.00) = 152.084, which rounds to 152.08.
7. Show the calculation of the molecular weight for C₈H₈NOI, reporting your answer to 2 places after the
decimal.
A) 261.05 g/mol
B) 259.00 g/mol
C) 263.10 g/mol
D) 260.05 g/mol
Correct Answer: 261.05 g/mol
Rationale: The calculation is: 8C (8 × 12.01 = 96.08) + 8H (8 × 1.008 = 8.064) + N (14.01) + O (16.00) + I
(126.90) = 261.054, which rounds to 261.05.
8. Calculate the number of moles in 12.0 grams of (NH₄)₂CrO₄. Report your answer to 3 significant
figures.
A) 0.0789 mole
Chemistry I w/Lab | Portage Learning | Q & A
| 2026 Edition
1. An atom or molecule that contains unequal numbers of protons and electrons is called a(n):
A) Isotope
B) Ion
C) Isomer
D) Nuclide
Correct Answer: Ion
Rationale: An ion is defined as an atom or molecule that has a net electrical charge because the total
number of electrons is not equal to the total number of protons. Isotopes have the same number of
protons but different neutrons, while isomers have the same formula but different structures.
2. Which subatomic particle has a relative mass of approximately 1 amu and a charge of 0?
A) Proton
B) Electron
C) Neutron
D) Positron
Correct Answer: Neutron
Rationale: A neutron has a mass of approximately 1 atomic mass unit (amu) and is electrically neutral
(charge of 0). Protons also have a mass of about 1 amu but carry a +1 charge, while electrons have
negligible mass and a -1 charge.
3. The modern periodic law states that the properties of elements are a periodic function of their:
A) Atomic mass
,B) Atomic number
C) Number of neutrons
D) Mass number
Correct Answer: Atomic number
Rationale: The modern periodic law states that the physical and chemical properties of elements are
periodic functions of their atomic numbers. Mendeleev's original table was based on atomic mass, but
Moseley's work established atomic number as the fundamental organizing principle.
4. Across a period from left to right, the atomic radius generally:
A) Increases
B) Decreases
C) Remains constant
D) Varies unpredictably
Correct Answer: Decreases
Rationale: Moving left to right across a period, protons are added to the nucleus, increasing the nuclear
charge. Electrons are added to the same principal energy level, so shielding remains relatively constant.
The increased effective nuclear charge pulls the electron cloud inward, decreasing atomic radius.
5. Which element has the largest atomic radius among the halogens?
A) Fluorine (F)
B) Chlorine (Cl)
C) Bromine (Br)
D) Iodine (I)
Correct Answer: Iodine (I)
, Rationale: Atomic radius increases as you move down a group because additional electron shells are
added. Among the halogens, iodine is at the bottom of Group 17 and therefore has the largest atomic
radius.
6. Show the calculation of the molecular weight for (NH₄)₂CrO₄, reporting your answer to 2 places after
the decimal.
A) 152.08 g/mol
B) 150.00 g/mol
C) 154.12 g/mol
D) 149.08 g/mol
Correct Answer: 152.08 g/mol
Rationale: The calculation is: 2N (2 × 14.01 = 28.02) + 8H (8 × 1.008 = 8.064) + Cr (52.00) + 4O (4 × 16.00
= 64.00) = 152.084, which rounds to 152.08.
7. Show the calculation of the molecular weight for C₈H₈NOI, reporting your answer to 2 places after the
decimal.
A) 261.05 g/mol
B) 259.00 g/mol
C) 263.10 g/mol
D) 260.05 g/mol
Correct Answer: 261.05 g/mol
Rationale: The calculation is: 8C (8 × 12.01 = 96.08) + 8H (8 × 1.008 = 8.064) + N (14.01) + O (16.00) + I
(126.90) = 261.054, which rounds to 261.05.
8. Calculate the number of moles in 12.0 grams of (NH₄)₂CrO₄. Report your answer to 3 significant
figures.
A) 0.0789 mole
