1.
In the Geiger-Marsden experiment, α particles are scattered by gold nuclei. The experimental results indicate that most α particles are
Correct Answer
A. Scattered only at small angles
Explanation
The Geiger-Marsden experiment involved scattering alpha particles off gold nuclei. The experimental results showed that most alpha particles were scattered only at small angles. This suggests that the gold nuclei have a positive charge concentrated in a small region, causing the alpha particles to be deflected by a small angle as they pass close to the nuclei. This observation supports the idea that atoms have a small, dense, positively charged nucleus, which was a significant finding in the development of the atomic model.
2.
A sample of radioactive carbon-14 decays into a stable isotope of nitrogen. As the carbon-14 decays, the rate at which the amount of nitrogen is produced.
Correct Answer
C. Decreases exponentially with time
Explanation
The decay of radioactive carbon-14 into a stable isotope of nitrogen follows an exponential decay model. This means that as time passes, the rate at which the amount of nitrogen is produced decreases exponentially. This is because the half-life of carbon-14 is constant, and as more time passes, the proportion of remaining carbon-14 atoms decreases. Therefore, the rate of nitrogen production decreases exponentially with time.
3.
Which one of the following provides direct evidence for the existence of discrete energy levels in an atom?
Correct Answer
B. The line emission spectrum of a gas at low pressure
Explanation
The line emission spectrum of a gas at low pressure provides direct evidence for the existence of discrete energy levels in an atom. When a gas at low pressure is excited, it emits light at specific wavelengths, creating a series of distinct colored lines in its spectrum. Each line corresponds to a specific energy level transition in the atoms of the gas. This observation supports the idea that electrons in atoms can only occupy certain discrete energy levels, and that they can transition between these levels by absorbing or emitting photons of specific energies.
4.
A sample of material initially contains atoms of only one radioactive isotope. Which one of the following quantities are reduced to one half of its initial value during a time equal to the half-life of the radioactive isotope?
Correct Answer
D. Activity of the radioactive isotope in the sample
Explanation
The activity of a radioactive isotope is a measure of the rate at which it decays, or the number of radioactive decays that occur per unit of time. The half-life of a radioactive isotope is the time it takes for half of the atoms in a sample to decay. Therefore, during a time equal to the half-life of the radioactive isotope, the activity of the isotope will also be reduced to one half of its initial value. This is because half of the atoms in the sample will have decayed, resulting in a decrease in the rate of radioactive decay and therefore a decrease in the activity of the isotope.
5.
In a fission chain reaction
Correct Answer
C. Neutrons from one fission reaction cause further fission reactions
Explanation
Neutrons from one fission reaction cause further fission reactions. In a fission chain reaction, the nucleus of an atom is split into two smaller nuclei, releasing a large amount of energy. This process also releases neutrons, which can then collide with other atomic nuclei, causing them to undergo fission as well. These new fission reactions release more energy and more neutrons, which continue the chain reaction. Therefore, it is the neutrons from one fission reaction that initiate and sustain further fission reactions in a chain reaction.
6.
Which one of the following correctly identifies the atomic (proton) number and mass (nucleon) number of a nucleus that has neutrons n and protons p?
Atomic number
Mass number
A.
p
n
B.
p
n + p
C.
n
p
D.
n + p
p
Correct Answer
B. B
Explanation
The correct answer is B because the atomic number (proton number) is represented by p, and the mass number (nucleon number) is represented by the sum of neutrons (n) and protons (p), which is n + p.
7.
Isotopes provide evidence for the existence of
Correct Answer
D. Neutrons
Explanation
Isotopes provide evidence for the existence of neutrons because isotopes are atoms of the same element that have different numbers of neutrons. This means that isotopes have the same number of protons and electrons, but different numbers of neutrons. By studying isotopes, scientists can determine the number of neutrons in an atom, which provides evidence for the existence of neutrons as a subatomic particle.
8.
An isotope of radium has a half-life of 4 days. A freshly prepared sample of this isotope contains N atoms. The time taken for 7N/8 of the atoms of this isotope to decay is
Correct Answer
C. 12 days
Explanation
The half-life of a radioactive substance is the time it takes for half of the atoms in a sample to decay. In this case, the half-life of the radium isotope is 4 days.
The decay of a radioactive substance follows an exponential decay law, which can be written as:
N(t)=N0​×(1/2)t/T
where:
N(t) is the number of atoms at time t,
N0​ is the initial number of atoms,
T is the half-life of the substance.
You want to find the time t when N(t)=N/8, which means 7N/8 of the atoms have decayed.
Setting up the equation gives us:
N/8=N×(1/2)t/4
Solving for t gives us:
t=4×log2​(8)=12 days
So, it will take 12 days for 7N/8 of the atoms of this isotope to decay.
9.
The presence of neutrons inside the nucleus is supported by the existence of
Correct Answer
A. Isotopes
Explanation
The presence of neutrons inside the nucleus is supported by the existence of isotopes. Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means that different isotopes of an element have different atomic masses. The existence of isotopes demonstrates that there must be particles other than protons present in the nucleus, since the atomic mass is not always equal to the number of protons. Therefore, the presence of isotopes supports the idea that neutrons exist within the nucleus.
10.
The source of the Sun’s energy is
Correct Answer
C. Fusion
Explanation
The correct answer is fusion. Fusion is the process in which two or more atomic nuclei come together to form a heavier nucleus, releasing a large amount of energy in the process. This is the source of the Sun's energy, as it fuses hydrogen nuclei to form helium, releasing a tremendous amount of energy in the form of light and heat. Fission, radioactivity, and ionization are not the correct answers as they do not accurately describe the source of the Sun's energy.
11.
The existence of isotopes provides evidence for the presence of
Correct Answer
C. Neutrons in the nuclei of atoms
Explanation
The existence of isotopes provides evidence for the presence of neutrons in the nuclei of atoms. Isotopes are atoms of the same element that have different numbers of neutrons. Since neutrons are found in the nucleus of an atom, the existence of isotopes suggests that there must be neutrons present in the nucleus. Electrons are found in atomic energy levels, not in the nucleus. Protons are also found in the nucleus, but the existence of isotopes does not specifically provide evidence for their presence.
12.
Ag-102, Ag-103, and Ag-104 are three isotopes of the element silver. Which one of the following is a true statement about the nuclei of these isotopes?
Correct Answer
D. All have the same number of protons
Explanation
Isotopes of an element have the same number of protons, as they belong to the same element. The number of protons determines the atomic number of an element. Therefore, Ag-102, Ag-103, and Ag-104 all have the same number of protons.
13.
Radioactive decay is a random process. This means that
Correct Answer
D. It cannot be predicted when a particular nucleus will decay
Explanation
Radioactive decay is a random process, meaning that it occurs spontaneously and cannot be predicted. While we can determine the average rate of decay for a large number of nuclei, we cannot predict when a specific nucleus will decay. This is due to the inherent uncertainty in quantum mechanics, which governs the behavior of individual particles. Therefore, it is not possible to determine the exact timing of decay for a particular nucleus.
14.
The number of nucleons in a nucleus is the number of
Correct Answer
D. Protons plus neutrons in the nucleus
Explanation
The number of nucleons in a nucleus refers to the total number of particles present in the nucleus. Nucleons include both protons and neutrons, so the correct answer is "protons plus neutrons in the nucleus". This answer accounts for both types of particles and gives a comprehensive count of all the nucleons in the nucleus.
15.
The emission and absorption spectra of different elements provides evidence for the existence of
Correct Answer
D. Atomic energy levels
Explanation
The emission and absorption spectra of different elements provide evidence for the existence of atomic energy levels. When an electron in an atom absorbs energy, it jumps to a higher energy level, and when it releases energy, it falls back to a lower energy level. Each energy level corresponds to a specific wavelength or color of light. The emission and absorption spectra show distinct lines or bands of colors, indicating the energy levels that electrons occupy in an atom. This observation supports the concept of atomic energy levels and their role in determining the behavior of electrons in atoms.
16.
The nucleus of an atom contains protons. The protons are prevented from flying apart by
Correct Answer
C. The presence of strong attractive nuclear forces
Explanation
The correct answer is the presence of strong attractive nuclear forces. These forces, also known as the strong nuclear force, are responsible for holding the protons together in the nucleus despite the repulsive forces between them due to their positive charges. Without these strong forces, the protons would repel each other and the nucleus would break apart. The presence of orbiting electrons and gravitational forces are not the main factors that prevent the protons from flying apart, and the absence of Coulomb repulsive forces is not accurate as these forces do exist but are counteracted by the strong nuclear forces.
17.
The unified mass unit is defined as the rest mass of
Correct Answer
B. An atom of carbon-12 divided by 12
Explanation
The unified mass unit is defined as the rest mass of an atom of carbon-12 divided by 12. This means that the mass of one atom of carbon-12 is divided by 12 to obtain the unified mass unit. This measurement is used to compare the masses of different particles and atoms on a unified scale, allowing for easier calculations and comparisons in the field of atomic and nuclear physics.
18.
Which one of the following provides evidence for a nuclear model of the atom?
Correct Answer
D. The scattering of alpHa particles by gold foil
Explanation
The scattering of alpha particles by gold foil provides evidence for a nuclear model of the atom. This experiment, conducted by Ernest Rutherford, involved firing alpha particles at a thin gold foil. According to the prevailing model at the time, the plum pudding model, the positive charge in the atom was thought to be spread out evenly throughout the atom. However, Rutherford's experiment showed that some alpha particles were deflected at large angles or even bounced back, indicating that the positive charge must be concentrated in a small, dense nucleus at the center of the atom. This observation supported the nuclear model of the atom.
19.
The main source of the Sun’s energy is
Correct Answer
C. Nuclear fusion
Explanation
The correct answer is nuclear fusion. Nuclear fusion is the process in which two or more atomic nuclei combine to form a heavier nucleus, releasing a large amount of energy. This is the main source of energy for the Sun and other stars. In the Sun's core, hydrogen nuclei combine to form helium, releasing a tremendous amount of energy in the process. This energy is what powers the Sun and allows it to emit light and heat.
20.
Which of the following identifies the significant interaction(s) between nucleons inside the nucleus?
Correct Answer
C. Nuclear and Coulomb
Explanation
The significant interactions between nucleons inside the nucleus are the nuclear and Coulomb interactions. The nuclear interaction is the strong force that holds the protons and neutrons together in the nucleus, while the Coulomb interaction is the electromagnetic force between the positively charged protons. These two interactions are responsible for the stability and structure of the nucleus. Gravitational force is negligible in comparison to the other forces and does not play a significant role in the interactions between nucleons inside the nucleus.
21.
A sample of a radioactive isotope of half-life T initially contains N atoms. Which one of the following gives the number of atoms of this isotope that have decayed after a time 3T?
Correct Answer
D. 7N/8
Explanation
After a time of 3T, the radioactive isotope will have gone through three half-lives. In each half-life, half of the atoms decay. Therefore, after three half-lives, only 1/8th (1/2 x 1/2 x 1/2) of the original number of atoms will remain. This means that 7/8th (1 - 1/8) of the atoms have decayed. Therefore, the number of atoms of this isotope that have decayed after a time 3T is 7N/8.
22.
Which one of the following correctly identifies the mass and momentum of a photon?
Mass
Momentum
A.
zero
zero
B.
zero
non-zero
C.
non-zero
zero
D.
non-zero
non-zero
Correct Answer
B. B
Explanation
A photon is a massless particle, meaning it has zero mass. However, a photon does have momentum, which is non-zero. This is because momentum is defined as the product of mass and velocity, and even though a photon has no mass, it still has velocity due to its wave-like nature. Therefore, the correct identification for the mass and momentum of a photon is zero and non-zero, respectively.
23.
Which of the following provides evidence for the existence of neutrons?
Correct Answer
B. Isotopes
Explanation
Isotopes provide evidence for the existence of neutrons because they are variants of an element that have the same number of protons but different numbers of neutrons. This indicates that there must be a neutral particle present in the nucleus of an atom, which is the neutron. By studying the different isotopes of an element and their properties, scientists have been able to gather evidence for the existence of neutrons.
24.
The atomic line spectra of elements provides evidence for the existence of
Correct Answer
D. Quantized energy states within atoms
Explanation
The atomic line spectra of elements refers to the specific wavelengths of light emitted or absorbed by atoms when they transition between energy levels. This phenomenon can only be explained by the existence of quantized energy states within atoms. These energy levels are discrete and distinct, meaning that electrons can only occupy certain energy levels and not the ones in between. This concept is a fundamental aspect of quantum mechanics and provides strong evidence for the existence of quantized energy states within atoms.
25.
Which of the following provides evidence for the existence of atomic energy levels?
Correct Answer
A. The absorption line spectra of gases
Explanation
The absorption line spectra of gases provide evidence for the existence of atomic energy levels. When light passes through a gas, certain wavelengths are absorbed by the gas atoms, resulting in dark lines in the spectrum. These lines correspond to specific energy transitions within the atoms, indicating that the energy levels of the atoms are quantized. This observation supports the idea that electrons in atoms can only occupy specific energy levels, and can transition between these levels by absorbing or emitting photons of specific energies.
26.
Which of the following statements best describes the random nature of radioactive decay?
Correct Answer
C. The time at which a particular nucleus will decay cannot be predicted
Explanation
The random nature of radioactive decay is best described by the statement that the time at which a particular nucleus will decay cannot be predicted. This means that there is no way to determine exactly when an individual nucleus will undergo decay. While the type of radiation emitted by the decaying nucleus can be predicted based on its decay mode, the timing of the decay event is inherently random and unpredictable. This randomness is a fundamental characteristic of radioactive decay and is not influenced by any external factors or environmental conditions.
27.
The Geiger-Marsden alpha particle scattering experiment provides evidence for the existence of
Correct Answer
A. Atomic nuclei
Explanation
The Geiger-Marsden alpha particle scattering experiment involved firing alpha particles at a thin gold foil. The observation that some of the alpha particles were deflected by large angles indicated the presence of a concentrated positive charge within the atom, which is now known as the atomic nucleus. This experiment provided evidence for the existence of atomic nuclei, as it showed that the majority of the atom's mass and positive charge is concentrated in a small, dense region at the center of the atom.
28.
A neutron is captured by a nucleus. Which of the following gives the changes in the atomic (proton) number and mass (nucleon) number of the nucleus?
Atomic number
Mass number
A.
unchanged
unchanged
B.
unchanged
increases by 1
C.
increases by 1
unchanged
D.
increases by 1
increases by 1
Correct Answer
B. B
Explanation
When a neutron is captured by a nucleus, it is converted into a proton. This means that the atomic (proton) number of the nucleus increases by 1. However, the mass (nucleon) number remains unchanged because a neutron and a proton have the same mass. Therefore, the correct answer is B, where the atomic number increases by 1 and the mass number remains unchanged.
29.
Which of the following provides evidence for the existence of atomic energy levels?
Correct Answer
D. Line absorption spectra
Explanation
Line absorption spectra provide evidence for the existence of atomic energy levels. When atoms absorb light, they transition from lower energy levels to higher energy levels. Each element has a unique set of energy levels, and when light passes through a sample of that element, it will absorb specific wavelengths corresponding to the energy differences between these levels. This results in dark lines, or absorption lines, in the spectrum. The presence of these lines confirms the existence of discrete energy levels in atoms and supports the concept of atomic energy levels.
30.
Nuclide X has a half-life of 1 day and nuclide Y has a half-life of 5 days. In a particular sample, the activities of X and Y are found to be equal.
When the activity is tested again after 10 days, the activity will be
Correct Answer
D. Mostly due to nuclide Y
Explanation
After 10 days, nuclide X would have undergone 10 half-lives, resulting in a decrease in activity by a factor of 2^10 (1024). On the other hand, nuclide Y would have undergone 2 half-lives, resulting in a decrease in activity by a factor of 2^2 (4). Since the initial activities of X and Y were equal, the activity after 10 days would be mostly due to nuclide Y, as it would have decayed at a slower rate compared to nuclide X.
31.
A nuclide X has a half-life of 10 s. On decay, the stable nuclide Y is formed. Initially, a sample contains only atoms of X. After what time will 87.5% of the atoms in the sample have decayed into nuclide Y.
Correct Answer
B. 30 s
Explanation
After one half-life, 50% of the atoms in the sample will have decayed into nuclide Y. Therefore, after two half-lives, 75% of the atoms will have decayed. Since the half-life of nuclide X is 10 s, two half-lives will take 20 s. However, the question asks for the time at which 87.5% of the atoms have decayed, which is closer to three half-lives. Therefore, the correct answer is 30 s, which is three times the half-life of nuclide X.
32.
Which of the following best describes why alpha-particles travel only a short distance in air?
Correct Answer
C. They ionize air molecules
Explanation
Alpha particles are positively charged particles consisting of two protons and two neutrons. When they pass through air, they have a strong tendency to ionize the air molecules. This means that they strip electrons from the atoms in the air, creating positively charged ions. This ionization process causes the alpha particles to lose energy rapidly, leading to a short travel distance in air. Therefore, the best description for why alpha particles travel only a short distance in air is that they ionize air molecules.
33.
Radioactive element P has a half-life of 30 days and element Q has a half-life of 20 days. Initially, a radioactive source contains equal numbers of each element.
What is the ratio number of atoms of P / number of atoms of Q after 60 days have elapsed?
Correct Answer
D. 2
Explanation
After 30 days, element P will have undergone one half-life, reducing the number of atoms by half. After 60 days, element P will have undergone two half-lives, reducing the number of atoms to one-fourth of the initial amount. Similarly, after 20 days, element Q will have undergone one half-life, reducing the number of atoms by half. After 60 days, element Q will have undergone three half-lives, reducing the number of atoms to one-eighth of the initial amount. Therefore, the ratio of the number of atoms of P to the number of atoms of Q after 60 days is 1/4 divided by 1/8, which equals 2.
34.
Monochromatic light is incident on a metal surface in a photocell. Which of the following statements is correct?
Correct Answer
A. The rate at which electrons are emitted from the surface is proportional to the intensity of the radiation
Explanation
The correct answer is that the rate at which electrons are emitted from the surface is proportional to the intensity of the radiation. This means that as the intensity of the incident light increases, the rate at which electrons are emitted from the metal surface also increases. This is because the energy of the incident photons determines the kinetic energy of the emitted electrons, and higher intensity light means more photons and therefore more energy available to transfer to the electrons.
35.
The initial activity of a sample of a radioactive isotope of half-life 10 hours is A. What is the age of the sample when its activity is A/32?
Correct Answer
C. 50 hours
Explanation
The half-life of a radioactive isotope is the time it takes for half of the initial activity to decay. In this case, the half-life is given as 10 hours. So, after 10 hours, the activity of the sample would be A/2. After another 10 hours (total of 20 hours), the activity would be A/4. Continuing this pattern, after 40 hours, the activity would be A/32, which matches the given activity. Therefore, the age of the sample when its activity is A/32 is 40 hours.
36.
Which one of the following correctly gives the number of electrons, protons and neutrons in a neutral atom of the nuclide
?
Number of electrons
Number of protons
Number of neutrons
A.
65
29
36
B.
36
36
29
C.
29
29
65
D.
29
29
36
Correct Answer
D. D
Explanation
The correct answer is D because a neutral atom has an equal number of electrons and protons. In this case, there are 29 electrons and 29 protons. The number of neutrons is not equal to the number of protons or electrons, so there are 36 neutrons in this atom.
37.
The unified mass unit is defined as
Correct Answer
B. 1/12 of the mass of one neutral atom of carbon-12
Explanation
The unified mass unit is defined as 1/12 of the mass of one neutral atom of carbon-12. This means that the mass of one carbon-12 atom is divided into 12 equal parts, and each part is considered as one unified mass unit. This standardizes the measurement of mass and allows for easy comparison between different atoms and molecules.
38.
The variation with thickness x of the number n of α-particles penetrating a material is shown below.
What can be deduced from the graph about the α-particles?
Correct Answer
A. The α-particles have approximately the same initial energy
Explanation
From the graph, it can be deduced that the α-particles have approximately the same initial energy. This is because the graph shows that the number of α-particles penetrating a material does not vary significantly with the thickness of the material. If the α-particles had different initial energies, there would be a noticeable variation in the number of particles penetrating the material at different thicknesses. However, since the graph shows a relatively constant number of particles, it suggests that the initial energy of the α-particles is approximately the same.
39.
Correct Answer
C. C
40.
In a laboratory when aluminium nuclei are bombarded with α-particles, the following reaction may take place.
This reaction is an example of
Correct Answer
D. Artificial transmutation
Explanation
Artificial transmutation refers to the process of changing one element into another by bombarding the nucleus with particles. In this case, when aluminium nuclei are bombarded with alpha particles, a new element is formed, indicating a change in the atomic number. Therefore, the given reaction is an example of artificial transmutation.
41.
In an α-particle scattering experiment (Geiger-Marsden experiment), the number n of particles incident per unit time on a detector was determined for different angles of deflection θ.
Which of the following graphs best shows the variation with θ of n?
Correct Answer
C. C
Explanation
The correct answer is C because it shows an inverse relationship between the number of particles incident per unit time (n) and the angle of deflection (θ). As the angle of deflection increases, the number of particles incident per unit time decreases. This is consistent with the findings of the Geiger-Marsden experiment, where it was observed that most α-particles passed straight through the gold foil with minimal deflection, while a small fraction experienced large deflections at larger angles.
42.
Correct Answer
A. A
43.
Correct Answer
A. Increased in magnitude because energy has been emitted from the nucleus
44.
Which of the following gives the correct number of protons and number of neutrons in the nucleus of
Number of protons
Number of neutrons
A.
5
6
B.
5
11
C.
6
5
D.
11
5
Correct Answer
A. A
Explanation
Option A states that the nucleus has 5 protons and 6 neutrons. The number of protons in an atom determines its atomic number, which in this case is 5. The number of neutrons is calculated by subtracting the atomic number from the mass number, which gives us 6 neutrons. Therefore, option A correctly provides the number of protons and neutrons in the nucleus.
45.
The graph below shows the variation with mass (nucleon) number of the average binding energy per nucleon.
Which direction indicates a fission reaction with a release of energy?
Correct Answer
D. IV
Explanation
Direction IV indicates a fission reaction with a release of energy. This is because as the mass (nucleon) number increases, the average binding energy per nucleon also increases. In a fission reaction, a heavy nucleus splits into two smaller nuclei, and this process releases energy. Therefore, as the mass number increases (as we move towards direction IV), the average binding energy per nucleon increases, indicating a fission reaction with a release of energy.
46.
When the isotope aluminium-27 is bombarded with alpha particles, the following nuclear reaction can take place.
Which one of the following correctly gives the atomic (proton) number and mass (nucleon) number of the nucleus X?
Proton number
Nucleon number
A.
15
30
B.
16
31
C.
30
15
D.
31
16
Correct Answer
A. A
Explanation
When aluminium-27 is bombarded with alpha particles, it can undergo a nuclear reaction in which an alpha particle (2 protons and 2 neutrons) is added to the aluminium-27 nucleus. This results in the formation of a new nucleus, X. Since an alpha particle has 2 protons, the proton number of nucleus X will be 13 (the original proton number of aluminium-27) + 2 = 15. The nucleon number of nucleus X will be 27 (the original nucleon number of aluminium-27) + 4 (2 protons and 2 neutrons from the alpha particle) = 30. Therefore, the correct answer is A.
47.
When the isotope aluminium-27 is bombarded with alpha particles, the following nuclear reaction can take place
Which one of the following correctly gives the atomic (proton) number and mass (nucleon) number of the nucleus X?
Proton number
Nucleon number
A.
15
30
B.
16
31
C.
30
15
D.
31
16
Correct Answer
A. A
Explanation
When aluminium-27 is bombarded with alpha particles, a nuclear reaction takes place. The atomic (proton) number of the resulting nucleus X is 15, which is the same as the atomic number of aluminium. The mass (nucleon) number of the resulting nucleus X is 30, which is the sum of the nucleon numbers of aluminium (27) and the alpha particle (2). Therefore, the correct answer is A.
48.
The nuclear notation for cadmium-114 is Which one of the following correctly shows the composition of this nucleus?
Number of protons
Number of neutrons
Number of nucleons
A.
48
66
114
B.
48
114
162
C.
66
48
114
D.
66
48
162
Correct Answer
A. A
Explanation
The correct answer is A. In the nuclear notation for cadmium-114, the number of protons is 48, the number of neutrons is 66, and the number of nucleons (protons + neutrons) is 114.
49.
Which one of the following diagrams best illustrates the first two stages of an uncontrolled fission chain reaction?
Correct Answer
B. B
Explanation
Diagram B best illustrates the first two stages of an uncontrolled fission chain reaction. In this diagram, a neutron is shown colliding with a uranium-235 nucleus, causing it to split into two smaller nuclei and releasing additional neutrons. These released neutrons can then go on to collide with other uranium-235 nuclei, creating a chain reaction. This diagram accurately represents the initial stages of an uncontrolled fission chain reaction, where the reaction is self-sustaining and can rapidly escalate.
50.
A nucleus of uranium-233 undergoes a- decay. Which of the following correctly identifies the number of protons Z and the number of neutrons N of the nucleus produced by this decay?
Z
N
A.
90
229
B.
90
139
C.
88
231
D.
88
141
Correct Answer
B. B
Explanation
In an alpha decay, the nucleus emits an alpha particle which consists of 2 protons and 2 neutrons. Therefore, the number of protons Z in the nucleus produced by this decay remains the same as the original nucleus (90), while the number of neutrons N decreases by 2, resulting in 139 neutrons. Therefore, the correct answer is B.