IB Chemistry Quiz: Apply The Nuclear Atom
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Apply The Nuclear AtomQuestion 1 of 20

Which statement best explains why the isotopes Chlorine-35 and Chlorine-37 have identical chemical properties?

They have the same number of neutrons, which determines chemical reactivity.
Their nuclei have the same overall charge, leading to similar electron shell repulsion.
They possess the same electron configuration, which dictates how they form chemical bonds.
Their different masses average out to a value that corresponds to a single set of chemical properties.
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IB Chemistry Quiz

IB Chemistry Quiz: Apply The Nuclear Atom

Practice Apply The Nuclear Atom in IB Chemistry with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Apply The Nuclear Atom, giving you a quick way to practice the rules, question types, and explanations that matter most for IB Chemistry.

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Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

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Question 1

Which statement best explains why the isotopes Chlorine-35 and Chlorine-37 have identical chemical properties?

  1. They have the same number of neutrons, which determines chemical reactivity.
  2. Their nuclei have the same overall charge, leading to similar electron shell repulsion.
  3. They possess the same electron configuration, which dictates how they form chemical bonds. (correct answer)
  4. Their different masses average out to a value that corresponds to a single set of chemical properties.
Explanation: Chemical properties of an element are determined by its electron configuration, specifically the valence electrons, as these are involved in bonding. Isotopes of an element have the same number of protons and therefore the same number of electrons in their neutral state, resulting in identical electron configurations and chemical properties. The number of neutrons (distractor A) affects mass but not chemical reactivity. Nuclear charge (distractor B) is determined by protons, which is correct, but the link to reactivity is the resulting electron configuration. Distractor D incorrectly describes the reason for their similar properties.

Question 2

Element Z has two naturally occurring isotopes. The lighter isotope, ⁸⁵Z, has a natural abundance of 72.0%. The relative atomic mass of Z is 85.56. What is the mass number of the other isotope?

  1. 86
  2. 87 (correct answer)
  3. 88
  4. 84
Explanation: Let the mass number of the heavier isotope be M. Its abundance is 100% - 72.0% = 28.0%. The relative atomic mass is the weighted average: (85 × 0.720) + (M × 0.280) = 85.56. This gives 61.20 + 0.280M = 85.56. Rearranging, 0.280M = 85.56 - 61.20 = 24.36. Solving for M: M = 24.36 / 0.280 = 87.

Question 3

Rubidium has a relative atomic mass of 85.47 and two major isotopes, ⁸⁵Rb and ⁸⁷Rb. In a mass spectrometer, the relative abundance of ions is proportional to the height of the peak. Which statement best describes the expected mass spectrum of rubidium?

  1. A single peak will be observed at m/z = 85.47.
  2. Two peaks of approximately equal height will be observed at m/z = 85 and m/z = 87.
  3. The peak at m/z = 87 will be significantly taller than the peak at m/z = 85.
  4. The peak at m/z = 85 will be significantly taller than the peak at m/z = 87. (correct answer)
Explanation: A mass spectrometer separates ions based on their mass-to-charge ratio. It does not measure the average mass. Since rubidium has two isotopes, two peaks will be seen at m/z values corresponding to their mass numbers (85 and 87). The relative atomic mass, 85.47, is much closer to 85 than to 87. This indicates that the ⁸⁵Rb isotope is much more abundant. Therefore, the peak corresponding to ⁸⁵Rb will be significantly taller.

Question 4

The element neon (Ne) has a relative atomic mass of approximately 20.2 and consists of isotopes with mass numbers 20, 21, and 22. What can be deduced from this information?

  1. The three isotopes are present in approximately equal abundances.
  2. The isotope ²⁰Ne is the most abundant. (correct answer)
  3. The isotope ²²Ne is the most abundant.
  4. The chemical reactivity of ²¹Ne is intermediate between that of ²⁰Ne and ²²Ne.
Explanation: The relative atomic mass is a weighted average of the isotopic masses. Since the relative atomic mass (20.2) is very close to 20, the isotope with mass number 20 must be the most abundant, heavily weighting the average towards its own mass. If the isotopes were in equal abundance (A), the average would be near 21. If ²²Ne were most abundant (C), the average would be closer to 22. Chemical reactivity (D) is the same for all isotopes.

Question 5

Two particles, P and Q, are isoelectronic. Particle P is an ion of element X with a charge of 2− and a mass number of 34. Particle Q is a neutral atom of a noble gas. If particle P has two more neutrons than protons, what is element X?

  1. Sulfur (correct answer)
  2. Chlorine
  3. Argon
  4. Phosphorus
Explanation: For particle P, let p be the number of protons and n be the number of neutrons. We are given: mass number = p + n = 34, and n = p + 2. Substituting the second equation into the first: p + (p + 2) = 34, which gives 2p = 32, so p = 16. The element with 16 protons is Sulfur (S). The information about particle Q (a noble gas with 18 electrons, Argon) is consistent, as S²⁻ also has 16+2=18 electrons, but the question asks for element X.

Question 6

A sample of naturally occurring gallium contains two isotopes, ⁶⁹Ga and ⁷¹Ga. The relative atomic mass of gallium is 69.72. What is the percentage abundance of the ⁶⁹Ga isotope?

  1. 28.0%
  2. 36.0%
  3. 64.0% (correct answer)
  4. 72.0%
Explanation: Let the fractional abundance of ⁶⁹Ga be x and that of ⁷¹Ga be (1-x). The relative atomic mass is the weighted average: (69 * x) + (71 * (1-x)) = 69.72. Solving for x: 69x + 71 - 71x = 69.72. This simplifies to -2x = -1.28. Therefore, x = 0.64. The percentage abundance is 0.64 * 100 = 64.0%.

Question 7

The relative atomic mass of chlorine is 35.45. Which is a valid conclusion that can be drawn from this fact alone?

  1. No individual chlorine atom has a mass of 35.45 u. (correct answer)
  2. Chlorine contains two isotopes, ³⁵Cl and ³⁷Cl, in a roughly 1:1 ratio.
  3. The most common isotope of chlorine has a mass number of 35.45.
  4. All chlorine atoms contain 18.45 neutrons in their nucleus.
Explanation: The relative atomic mass is a weighted average of the masses of the isotopes. Since it is not a whole number, it cannot represent the mass of a single atom (which must have an integer number of protons and neutrons). Therefore, no single chlorine atom can have a mass of 35.45 u. B is incorrect because the ratio is closer to 3:1, not 1:1. C and D are incorrect because mass numbers and neutron counts must be integers.

Question 8

Two atoms have the same number of electrons but different numbers of neutrons. One atom has 18 protons and the other has 17 protons. What is the difference in their charges?

  1. The atom with 18 protons has a charge that is 1 more positive than the other atom (correct answer)
  2. The atom with 17 protons has a charge that is 1 more negative than the other atom
  3. Both atoms have the same charge since they have the same number of electrons
  4. The difference in charge depends on the specific number of neutrons in each atom
Explanation: Charge = protons - electrons. Since both atoms have the same number of electrons but one has 18 protons while the other has 17, the difference in charge is 18 - 17 = 1. The atom with 18 protons is more positive by 1. Choice B states the relationship backwards. Choice C ignores the proton difference. Choice D incorrectly suggests neutrons affect charge.

Question 9

A sample contains atoms of the same element with mass numbers 79 and 81. If the average atomic mass of this sample is 79.6 u, and the atomic number is 35, what is the ratio of neutrons in the heavier isotope to neutrons in the lighter isotope?

  1. 46:44, representing a neutron difference that accounts for the mass variation between isotopes (correct answer)
  2. 44:46, indicating that the lighter isotope actually contains more neutrons per nucleus
  3. 81:79, reflecting the direct relationship between mass number and neutron count in isotopes
  4. 23:22, showing the neutron excess above the atomic number for each respective isotope
Explanation: For atomic number 35: lighter isotope (mass 79) has 79-35=44 neutrons; heavier isotope (mass 81) has 81-35=46 neutrons. Ratio of heavier to lighter is 46:44. Choice B reverses the ratio. Choice C uses mass numbers instead of neutron counts. Choice D incorrectly calculates some other relationship.

Question 10

A research team is studying the nuclear composition of various atoms. They observe that atom M has the same number of neutrons as atom N, but atom M has 2 fewer protons than atom N. Additionally, atom M has gained 1 electron while atom N has lost 2 electrons from their neutral states.

Based on the information in the passage, what is the difference in charge between atoms N and M?

  1. Atom N has a charge that is 5 units more positive than atom M's charge (correct answer)
  2. Atom N has a charge that is 3 units more positive than atom M's charge
  3. Atom N has a charge that is 1 unit more positive than atom M's charge
  4. Atom M has a charge that is 1 unit more positive than atom N's charge
Explanation: Let atom M have p protons originally, so atom N has p+2 protons. From their neutral states: M gains 1 electron (charge = p - (p+1) = -1), while N loses 2 electrons (charge = (p+2) - (p+2-2) = (p+2) - p = +2). The difference in charge is: N's charge - M's charge = (+2) - (-1) = +3. However, we must also account for N having 2 more protons than M originally. Total difference: 2 (extra protons) + 3 (electron changes) = 5 units more positive for N.

Question 11

Which property is expected to be slightly different for the isotopes ²⁰Ne and ²²Ne?

  1. The number of electrons in the valence shell.
  2. The atomic number.
  3. The rate of diffusion in the gaseous state. (correct answer)
  4. The charge of the nucleus.
Explanation: Isotopes of an element have the same number of protons and electrons, so their atomic number, nuclear charge, and electron configuration (including valence electrons) are identical. This results in identical chemical properties. However, they have different numbers of neutrons and therefore different masses. Physical properties that depend on mass, such as density, vibrational frequency, and rate of diffusion (as described by Graham's Law), will be different. The lighter isotope, ²⁰Ne, will diffuse faster than the heavier isotope, ²²Ne.

Question 12

The relative atomic mass of boron is 10.81. It has two stable isotopes, ¹⁰B and ¹¹B. What can be deduced about a random sample of 1000 boron atoms?

  1. The sample will contain approximately 190 ¹⁰B atoms and 810 ¹¹B atoms. (correct answer)
  2. The sample will contain approximately 810 ¹⁰B atoms and 190 ¹¹B atoms.
  3. The sample will contain exactly 500 atoms of each isotope.
  4. The mass of every atom in the sample will be 10.81 u.
Explanation: The relative atomic mass (10.81) is a weighted average. Since 10.81 is much closer to 11 than to 10, the isotope ¹¹B must be significantly more abundant. Let abundance of ¹¹B be x. 11x + 10(1-x) = 10.81 => x = 0.81. So, ¹¹B is ~81% abundant and ¹⁰B is ~19% abundant. In a 1000-atom sample, one would expect about 810 ¹¹B atoms and 190 ¹⁰B atoms.

Question 13

Which of the following species contains the same number of neutrons as an atom of ⁸⁰₃₅Br?

  1. ⁸⁰₃₆Kr
  2. ⁷⁹₃₅Br
  3. ⁸⁰₃₄Se
  4. ⁸¹₃₆Kr (correct answer)
Explanation: First, calculate the number of neutrons in ⁸⁰₃₅Br: Neutrons = Mass Number (A) - Atomic Number (Z) = 80 - 35 = 45. Now, calculate the number of neutrons for each option: A) ⁸⁰₃₆Kr: 80 - 36 = 44 neutrons. B) ⁷⁹₃₅Br: 79 - 35 = 44 neutrons. C) ⁸¹₃₆Kr: 81 - 36 = 45 neutrons. D) ⁸⁰₃₄Se: 80 - 34 = 46 neutrons. Therefore, ⁸¹₃₆Kr has the same number of neutrons as ⁸⁰₃₅Br.

Question 14

A neutral atom of an element has an atomic number Z and a mass number A. Which statement is always correct for any neutral isotope of this element?

  1. The atom contains A electrons.
  2. The nucleus contains A-Z protons.
  3. The nucleus has a different number of protons.
  4. The atom has the same chemical reactivity. (correct answer)
Explanation: Isotopes of an element have the same atomic number (Z), meaning they have the same number of protons. For a neutral atom, the number of electrons also equals Z. Since chemical reactivity is determined by the electron configuration, all isotopes of an element have identical chemical reactivity. A is incorrect; it has Z electrons. B is incorrect; it has Z protons. D is incorrect by definition.

Question 15

The mass of one atom of a specific isotope is 12.000 u by definition. What is this isotope?

  1. Hydrogen-1
  2. Helium-4
  3. Oxygen-16
  4. Carbon-12 (correct answer)
Explanation: The unified atomic mass unit (u) is defined as exactly one-twelfth of the mass of a single, neutral atom of carbon-12 in its nuclear and electronic ground state. Therefore, the mass of one carbon-12 atom is exactly 12.000 u by definition. This serves as the standard for all other atomic mass measurements.

Question 16

The nucleus of an atom of element Y contains p protons and n neutrons. The atom loses two electrons. What is the composition of the resulting ion?

  1. p protons, n neutrons, p+2 electrons
  2. p-2 protons, n neutrons, p-2 electrons
  3. p protons, n neutrons, p-2 electrons (correct answer)
  4. p protons, n-2 neutrons, p electrons
Explanation: The nucleus is unaffected by the loss of electrons, so the number of protons (p) and neutrons (n) remains the same. A neutral atom has the same number of electrons as protons, which is p. When the atom loses two electrons, the number of electrons becomes p-2. The resulting ion has p protons, n neutrons, and p-2 electrons.

Question 17

An ion X³⁺ has a mass number of 52 and contains 21 electrons. What are the numbers of protons and neutrons in a neutral atom of this element?

  1. 21 protons and 31 neutrons
  2. 24 protons and 28 neutrons (correct answer)
  3. 24 protons and 52 neutrons
  4. 21 protons and 28 neutrons
Explanation: The ion has a 3+ charge and 21 electrons. This means it has lost 3 electrons from its neutral state. Therefore, a neutral atom of element X has 21 + 3 = 24 electrons. In a neutral atom, the number of protons equals the number of electrons, so there are 24 protons. The number of neutrons is the mass number minus the atomic number (number of protons), which is 52 - 24 = 28 neutrons.

Question 18

How many protons, neutrons, and electrons are present in the selenide ion, ⁷⁹₃₄Se²⁻?

  1. 34 protons, 45 neutrons, 32 electrons
  2. 34 protons, 45 neutrons, 36 electrons (correct answer)
  3. 34 protons, 79 neutrons, 36 electrons
  4. 45 protons, 34 neutrons, 36 electrons
Explanation: The notation ⁷⁹₃₄Se²⁻ provides all the necessary information. The atomic number (bottom number, Z) is 34, which is the number of protons. The mass number (top number, A) is 79. The number of neutrons is A - Z = 79 - 34 = 45. The charge is 2-, meaning the neutral atom has gained 2 electrons. A neutral Se atom has 34 electrons, so the ion has 34 + 2 = 36 electrons.

Question 19

Consider the three species: ⁴⁰Ca²⁺, ³⁹K, and ⁴¹K⁺. Which species possess the same number of electrons, and which possess the same number of neutrons, respectively?

  1. Same electrons: ⁴⁰Ca²⁺ and ³⁹K; Same neutrons: ³⁹K and ⁴¹K⁺
  2. Same electrons: ³⁹K and ⁴¹K⁺; Same neutrons: ⁴⁰Ca²⁺ and ³⁹K
  3. Same electrons: ⁴⁰Ca²⁺ and ⁴¹K⁺; Same neutrons: ⁴⁰Ca²⁺ and ³⁹K (correct answer)
  4. Same electrons: ⁴⁰Ca²⁺ and ⁴¹K⁺; Same neutrons: ³⁹K and ⁴¹K⁺
Explanation: First, determine the composition of each species:
  • ⁴⁰Ca²⁺ (Z=20): 20p, 20n, 18e⁻ (20-2)
  • ³⁹K (Z=19): 19p, 20n, 19e⁻
  • ⁴¹K⁺ (Z=19): 19p, 22n, 18e⁻ (19-1) Species with the same number of electrons (isoelectronic) are ⁴⁰Ca²⁺ and ⁴¹K⁺ (both have 18). Species with the same number of neutrons (isotones) are ⁴⁰Ca²⁺ and ³⁹K (both have 20).

Question 20

A beam containing three species, P (²⁰Ne), Q (²²Ne), and R (²⁰Ne⁺), is passed through a uniform electric field. Which statement correctly describes their behaviour?

  1. All three species will be deflected, with Q being deflected the least.
  2. Only R will be deflected, while P and Q pass through undeflected. (correct answer)
  3. P and R will be deflected by the same amount because they have the same mass.
  4. P and Q will be deflected in opposite directions to R.
Explanation: An electric field exerts a force on charged particles. Species P (²⁰Ne) and Q (²²Ne) are neutral atoms and will not be affected by the electric field, so they will pass through undeflected. Species R (²⁰Ne⁺) has a positive charge, so it will be deflected by the electric field. Therefore, only R is deflected.