Isotopes
Choose the best answer from the options that follow each question.
____
1. Neutral atoms contain equal numbers of
a. electrons and neutrons.
b. protons and neutrons.
c. protons and electrons.
d. protons, electrons, and neutrons.
____
2. The atomic symbol for beryllium,
, indicates that the
a. atomic number is 4.
b. atomic number is 9.
c. mass number is 4.
d. atomic number is equal to 9 4.
____
3. The atomic mass of an atom of carbon is 12 amu, and the atomic mass of an atom of oxygen is 16 amu. To
produce CO2, 16 g of oxygen combine with 12 g of carbon. To produce CO2, 32 g of oxygen combine with
12 g of carbon. The ratio of the mass of oxygen in CO2 to the mass of oxygen in CO is
a. 1:1.
b. 2:1.
c. 1:2.
d. 8:3.
____
4. Rutherford’s gold-foil experiment led him to conclude that
a. Thomson’s plum pudding model of the atom was accurate.
b. alpha particles were a poor choice for a bombardment material.
c. a dense region of positive charge existed somewhere in the atom.
d. light was emitted by electrons returning to ground state.
____
5. Which of the following is not one of the five principles of Dalton’s theory?
a. Atoms of different elements combine in simple, whole-number ratios to form compounds.
b. All matter is made of indivisible, indestructible atoms.
c. All atoms have similar physical and chemical properties.
d. Chemical reactions consist of the combination, separation, or rearrangement of atoms.
____
6. According to the law of definite proportions, any two samples of KCl will have
a. the same mass.
b. slightly different molecular structures but the same two elements.
c. different densities.
d. the same elements in the same proportions by mass.
____
7. According to the law of conservation of mass, when sodium, hydrogen, and oxygen react to form a
compound, the mass of the compound will be
a. equal to the sum of the masses of the reactants.
b. greater than the sum of the masses of the reactants.
c. less than the sum of the masses of the reactants.
d. either less than or equal to the sum of the masses of the reactants.
____
8. Thomson’s experiment showed that the charge-to-mass ratio of electrons was
a. greater with noble gases than for other gases.
b. less with noble gases than for other gases.
c. the same in all gases.
d. dependent on the element’s atomic mass.
____
9. An atom of potassium has 19 protons and 20 neutrons. Its mass number is
a. 9.
b. 19.
c. 20.
d. 39.
____ 10. Which of the following is not equal to 1.00 mol of carbon-12?
a. 6.022 1023 carbon atoms
b. 12.0 g of carbon
c. 6.0 g of carbon
d. Both (b) and (c)
____ 11. Compared with a mole of lead atoms, a mole of iron atoms
a. has more atoms.
b. has fewer atoms.
c. has the same number of atoms.
d. cannot be determined because iron is magnetic.
____ 12. The molar mass of an element is numerically equal to
a. the element’s average atomic mass.
b. the element’s average atomic number.
c. the number of electrons possessed by an element.
d. the percentage composition of the element by mass.
____ 13. To calculate the number of atoms present in 2.0 mol of an element, you would
a. add Avogadro’s number of atoms per mole to 2.0 mole.
b. subtract Avogadro’s number of atoms per mole from 2.0 mole.
c. multiply Avogadro’s number of atoms per mole by 2.0 mole.
d. divide Avogadro’s number of atoms per mole by 2.0 mole.
____ 14. The units of molar mass are
a. g/mol.
b. mol/g.
c. amu/mol.
d. amu/g.
____ 15. To determine the mass in grams of an atom of any element, you would
a. multiply the mass of a mole of the element by Avogadro’s number.
b. divide the mass of a mole of the element by Avogadro’s number.
c. add the mass of a mole of the element to Avogadro’s number.
d. subtract the mass of a mole of the element from Avogadro’s number.
____ 16. The average atomic mass of an element is
a. the mass of one isotope of the element.
b. the weighted average of all naturally occurring isotopes of the element.
c. the same as the atomic number of the element.
d. the sum of the number of neutrons and protons in an atom.
____ 17. The ancient Greek natural philosopher who first proposed the notion of the atom was
a. Aristotle.
b. Socrates.
c. Democritus.
d. Plato.
____ 18. The word atom means
a. indivisible.
b. indestructible.
c. energetic.
d. charged.
____ 19. Which feature of Dalton’s atomic theory is different from modern atomic theory?
a. Atoms cannot be destroyed.
b. Atoms cannot be subdivided.
c. Atoms cannot be rearranged in chemical reactions.
d. Atoms combine in whole-number ratios.
____ 20. The molecular mass of CO2 is 44.01 amu. What is the mass of 2.0 mol of CO2?
a. 44.01 amu
b. 44.01 g
c. 88.02 amu
d. 88.02 g
____ 21. The least massive particle in an atom is the
a. proton.
b. neutron.
c. electron.
d. None of the above
____ 22. The most massive particle in an atom is the
a. proton.
b. neutron.
c. electron.
d. None of the above
____ 23. Protons are bound together by
a. electric forces.
b. magnetic forces.
c. strong nuclear forces.
d. gravitational forces.
____ 24. How many moles of sodium hydroxide, NaOH, are in a 35.65 g sample of NaOH? (The molar mass of NaOH
is 40.01 g/mol.)
a. 0.8910 mol
b. 1.122 mol
c. 1426 mol
d. 5.366 1023 mol
____ 25. What is the mass of 3.56 mol of glucose, C6H12O6? (The molar mass of`C6H12O6 is 180.18 g/mol.)
a. 50.6 g
b. 641 g
c. 0.0198 g
d. 2.14 1024 g
PART I Choose the best answer from the options that follow each question.
____ 26. The behavior of cathode rays in a glass tube containing gas at low pressure led scientists to conclude that the
rays are composed of
a. energy.
b. positive particles.
c. negative particles.
d. neutral particles.
____ 27. The basic principles of atomic theory were first conceived by
a. Avogadro.
b. Bohr.
c. Dalton.
d. Rutherford.
____ 28. The law of multiple proportions is demonstrated by the compounds
a. FeCl3 and Fe(SO4)3.
b. O2 and O3.
c. CO and CO2.
d. FeCl2 and Fe(NO3)2.
____ 29. Neutral atoms of the same element can differ in
a. chemical properties.
b. mass number.
c. atomic number.
d. number of protons and electrons.
____ 30. Dalton’s atomic theory helped to explain the law of conservation of mass because it stated that atoms
a. cannot combine.
b. are indivisible.
c. all have the same mass.
d. cannot be created or destroyed.
____ 31. Millikan’s experiments led to the determination
a. that the electron carries no charge.
b. of the electron’s positive charge.
c. of the approximate value of the electron’s mass.
d. that the electron has no mass.
____ 32. The discovery of the nucleus was a result of Rutherford’s observation that a small percentage of the positively
charged particles bombarding the metal’s surface
a. were slightly deflected as they passed through the metal.
b. were deflected back toward the source.
c. passed straight through the metal.
d. combined with the metal.
____ 33. Most of the volume of an atom is occupied by the
a. nucleus.
b. nuclides.
c. electrons.
d. protons.
PART II Write the correct term (or terms) in the space provided.
34. If a particular compound is composed of elements A and B, the ratio of the mass of B to the mass of A will
always be the same. This is a statement of the law of ____________________.
35. The amount of a substance that contains a number of particles equal to the number of atoms in exactly 12 g of
carbon-12 is referred to as a(n) ____________________.
36. Because any metal cathode used in a cathode-ray tube produces the same charged particles, it was concluded
that all atoms contain ____________________.
37. The smallest particle of an element that retains the chemical properties of that element is a(n)
____________________.
38. Atoms of one element that have different masses are called ____________________.
39. The total number of protons and neutrons in the nucleus of an isotope is called its ____________________
number.
40. The short-range attractive forces that hold the nuclear particles together are called ____________________.
41. The number of protons in the nucleus of an element is called its ____________________ number.
42. If two or more compounds are composed of elements A and B, the ratio of the masses of B combined with 1 g
of A is always a ratio of small whole numbers. This is a statement of the law of ____________________.
43. Dalton’s theory agreed with the modern atomic theory in almost all cases. List the two statements that were
later found to be in error. ________________________________________
PART III Complete the following tables to compare the types of subatomic particles.
44.
Particle
Proton
Mass number
Relative charge
Location
Particle
Neutron
Mass number
Relative charge
Location
Particle
Electron
Mass number
Relative charge
Location
45.
46.
PART IV Write the answers to the following questions in the space provided.
47. State three of the main concepts in Dalton’s atomic theory.
48. What is molar mass? How is it related to atomic mass?
49. Explain why the atomic mass of a particular isotope of an element differs from the average atomic mass of
that element.
PART V Write the answers to the questions below, and show your work in the space provided.
50. The atomic number of nickel-60 is 28. How many neutrons does this isotope have?
51. Carbon-14 has 8 neutrons. What is the atomic number of carbon-14?
52. A neutral atom of silicon-30 contains 14 protons. How many electrons does it have?
53. Oxygen has three naturally occurring isotopes in the following proportions: oxygen-16, 99.762% (15.994 91
amu); oxygen-17, 0.038000% (16.999 13 amu); oxygen-18, 0.20000% (17.999 16 amu). What is the average
atomic mass of oxygen?
54. The average atomic mass of chromium is 52.00 amu. What is the mass of 3.00 mol of chromium?
55. How many moles are in a 63.60 g sample of carbon? (The molar mass of carbon is 12.01 g/mol.)
56. The mass of a sample of nickel (average atomic mass 58.69 amu) is 11.74 g. How many atoms does it
contain?
57. The atomic mass of sulfur is 32.06 amu. How many atoms are present in exactly 2 mol of sulfur?
Choose the best answer from the options that follow each question.
____ 58. The atomic number of an element is
a. the mass of the element.
b. 1 mol of the element.
c. the number of protons in each atom of the element.
d. the number of neutrons in each atom of the element.
____ 59. Hydrogen that is composed of atoms with two neutrons is called
a. protium.
b. deuterium.
c. tritium.
d. helium.
____ 60. Isotopes are atoms of the same element that have different
a. masses.
b. charges.
c. numbers of electrons.
d. atomic numbers.
____ 61. Mass number is
a. the average atomic mass of an element.
b. the total number of electrons in an atom of an element.
c. the total number of protons in an atom of an element.
d. the total number of protons and neutrons in an atom of an element.
____ 62. The isotope uranium-235 has 92 protons and 143 neutrons. Therefore, its mass number is
a.
b.
c.
d.
92.
235.
143.
impossible to determine.
____ 63. The nuclear symbol for uranium-235 should be written as
a. U-235.
b.
U
c.
U
d. U
____ 64. What is the definition of one atomic mass unit?
a. 1 g of any element
b. 1 mol of any element
c.
of the mass of a carbon-12 atom
d.
of the mass of any atom
____ 65. To take a weighted average of all the naturally occurring isotopes of an element in order to arrive at an
average atomic mass, you would
a. multiply the mass of each isotope by the decimal fraction representing its abundance
naturally, then add all these products together.
b. use the isotope with the largest mass.
c. use the isotope with the most average mass.
d. add all the masses of all of the isotopes, then divide by the number of isotopes.
____ 66. One mole is defined as
a. the volume of a substance with a mass of 12 g.
b. the amount of a substance that contains as many particles as there are atoms in exactly 12
g of carbon-12.
c. the amount of a substance that contains as many particles as there are atoms in exactly 12
g of silver.
d. an amount of a substance that contains enough atoms to have a mass of 12 g.
____ 67. The molar mass of an element is numerically equal to the element’s
a. average number of electrons.
b. average number of protons.
c. average atomic mass.
d. average atomic number.
Isotopes
Answer Section
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definite proportions
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35. ANS: mole
TOP: Chapter 3 Test B
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36. ANS: electrons
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37. ANS: atom
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38. ANS: isotopes
TOP: Chapter 3 Test B
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39. ANS: mass
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40. ANS: nuclear forces
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41. ANS: atomic
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42. ANS: multiple proportions
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43. ANS: All atoms of the same element have the same mass; atoms cannot be subdivided.
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44. ANS:
TOP: Chapter 3 Test B
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45. ANS:
in the nucleus
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in the nucleus
1–
outside the nucleus
(in the electron
cloud)
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47. ANS:
Answers should include three of the following:
All matter is composed of extremely small particles called atoms.
All atoms of an element are identical in size, mass, and other properties; atoms of different elements differ in
size, mass and other properties.
Atoms cannot be subdivided, created, or destroyed.
Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
In chemical reactions, atoms are combined, separated, or rearranged.
PTS: 1
TOP: Chapter 3 Test B
48. ANS:
The molar mass of a substance is the mass of one mole of the substance. A mole of any substance contains
6.022137 1023 particles, or Avogadro’s number of particles. The atomic mass is the mass of one atom.
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49. ANS:
TOP: Chapter 3 Test B
The atomic mass of a single isotope of an element is its relative mass compared to the mass of carbon-12. The
average atomic mass of an element is the weighted average of the masses of all naturally occurring isotopes of
an element.
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50. ANS:
32
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51. ANS:
6
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52. ANS:
14
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53. ANS:
15.999 amu
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54. ANS:
156 g
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55. ANS:
5.296 mol
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56. ANS:
1.205 1023 atoms
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57. ANS:
1.204 1024 atoms
TOP: Chapter 3 Test B
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Chapter 3 - Section Quiz 3
Chapter 3 - Section Quiz 3
Chapter 3 - Section Quiz 3
Chapter 3 - Section Quiz 3
Chapter 3 - Section Quiz 3
Chapter 3 - Section Quiz 3
Chapter 3 - Section Quiz 3
Chapter 3 - Section Quiz 3
Chapter 3 - Section Quiz 3
Chapter 3 - Section Quiz 3