Question 1

Which of the following best explains why the atomic mass of chlorine listed on the periodic table is not a whole number?
Correct answer: It is a weighted average of the masses of all naturally occurring isotopes of chlorine.

Accepted Answer

It is a weighted average of the masses of all naturally occurring isotopes of chlorine.

Question 2

A forensic scientist is analyzing a sample of tooth enamel to determine the age of a skeleton. Which property of atoms is most directly useful for this analysis?
Correct answer: The ratio of isotopes, such as 14C to 12C, present in the sample

Accepted Answer

The ratio of isotopes, such as 14C to 12C, present in the sample

Question 3

Which statement about isotopes is correct?
Correct answer: Isotopes of an element have the same number of protons but different numbers of neutrons.

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 4

A sample of element X contains two naturally occurring isotopes: X-29 (mass = 29.0 u, abundance = 60%) and X-30 (mass = 30.0 u, abundance = 40%). What is the average atomic mass of element X?
Correct answer: 29.4 u

Accepted Answer

29.4 u

Question 5

Which experiment or law first demonstrated that the total mass remains constant during a chemical reaction?
Correct answer: Lavoisier's law of conservation of mass

Accepted Answer

Lavoisier's law of conservation of mass

Question 6

A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many neutrons does it contain?
Correct answer: 12

Accepted Answer

12

Question 7

Which of the following statements about Dalton’s atomic theory is NOT consistent with modern understanding?
Correct answer: Atoms are indivisible and indestructible.

Accepted Answer

Atoms are indivisible and indestructible.

Question 8

A mass spectrometer is used to analyze a sample of neon. What information can be directly obtained from the resulting mass spectrum?
Correct answer: The relative abundances and masses of neon isotopes

Accepted Answer

The relative abundances and masses of neon isotopes

Question 9

Which of the following best describes the structure of an atom according to modern atomic theory?
Correct answer: A dense nucleus containing protons and neutrons, with electrons moving in the mostly empty space around it

Accepted Answer

A dense nucleus containing protons and neutrons, with electrons moving in the mostly empty space around it

Question 10

Which change would result in the formation of a different element?
Correct answer: Changing the number of protons in the nucleus

Accepted Answer

Changing the number of protons in the nucleus

Question 11

A sample of carbon contains 98.9% 12C (mass = 12.000 u) and 1.1% 13C (mass = 13.003 u). What is the average atomic mass of carbon? (Round to three decimal places.)
Correct answer: 12.011 u

Accepted Answer

12.011 u

Question 12

Which of the following real-world applications relies on the law of definite proportions?
Correct answer: Determining the purity of a pharmaceutical compound by analyzing its elemental composition

Accepted Answer

Determining the purity of a pharmaceutical compound by analyzing its elemental composition

Question 13

An atom has 17 protons, 18 neutrons, and 17 electrons. What is its mass number and what element is it?
Correct answer: Mass number 35, element chlorine

Accepted Answer

Mass number 35, element chlorine

Question 14

Which of the following best describes the difference between protons and neutrons?
Correct answer: Protons have a positive charge, neutrons have no charge; both have nearly the same mass.

Accepted Answer

Protons have a positive charge, neutrons have no charge; both have nearly the same mass.

Question 15

Which scenario would violate the law of conservation of mass?
Correct answer: A chemical reaction in which the total mass of products is less than the total mass of reactants

Accepted Answer

A chemical reaction in which the total mass of products is less than the total mass of reactants

Question 16

Which of the following is a correct application of Dalton’s atomic theory to explain why water always has the same ratio of hydrogen to oxygen by mass?
Correct answer: Water is composed of hydrogen and oxygen atoms combined in a fixed, small whole-number ratio.

Accepted Answer

Water is composed of hydrogen and oxygen atoms combined in a fixed, small whole-number ratio.

Question 17

A neutral atom of element Q has 20 protons and 22 neutrons. If it gains two electrons, what is its resulting charge?
Correct answer: 2-

Accepted Answer

2-

Question 18

Which of the following best explains why isotopic analysis is important in archaeology?
Correct answer: It allows scientists to date artifacts by measuring the ratios of specific isotopes.

Accepted Answer

It allows scientists to date artifacts by measuring the ratios of specific isotopes.

Question 19

Which of the following statements about electrons is correct?
Correct answer: Electrons are negatively charged and have much less mass than protons or neutrons.

Accepted Answer

Electrons are negatively charged and have much less mass than protons or neutrons.

Atomic Structure and Nuclear Chemistry: Key Concepts

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