Chapter 30: Nuclear Physics and Radioactivity

The atomic mass number represents the total number of protons and neutrons in an atom. The atomic number represents the number of protons in an atom. To find the number of neutrons, subtract the atomic number from the atomic mass number. In this case, the element has an atomic number of 6 and an atomic mass number of 14. Subtracting 6 from 14 gives us 8, which is the number of neutrons in the atom.

Isotopes are atoms of the same element that have the same number of protons (atomic number) but different numbers of neutrons. This means that isotopes have different mass numbers, which is the total number of protons and neutrons in the nucleus. Isotopes have similar chemical properties but may have different physical properties due to their different mass numbers. Therefore, the correct answer is "isotopes."

The electron has the least mass among the atomic particles. This is because electrons are subatomic particles that orbit around the nucleus of an atom, and they have a very small mass compared to protons and neutrons. Protons and neutrons are located in the nucleus and are much larger and heavier in comparison. Therefore, the electron is the correct answer as it has the least mass.

The number of protons in an atom is equal to the number of electrons. This is because protons have a positive charge, while electrons have a negative charge. In a neutral atom, the number of protons is balanced by the number of electrons, resulting in no overall charge. This balance between protons and electrons determines the atomic number of an element, which is unique for each element. Therefore, the number of protons in an atom is always equal to the number of electrons.

The atomic number of an element represents the number of protons in its nucleus. Since the atomic number of the element is given as 15, it means that the number of protons in the nucleus is 15. The mass number of an element represents the total number of protons and neutrons in its nucleus. It is given that the isotope has a mass number of 32. Therefore, the number of neutrons in the nucleus can be calculated by subtracting the atomic number from the mass number: 32 - 15 = 17. Hence, the correct answer is "the number of neutrons in the nucleus is 17."

Isotopes of an element have nuclei with the same number of protons, but different numbers of neutrons. This means that the atomic number, which is determined by the number of protons, remains the same for all isotopes of an element. However, the mass number, which is determined by the number of protons and neutrons combined, varies among isotopes. Therefore, isotopes have the same number of protons, but different numbers of neutrons.

When an atom undergoes alpha decay, it emits an alpha particle, which consists of two protons and two neutrons. Therefore, the daughter nucleus will have two fewer protons than the original atom. Since the original atom has 98 protons, the daughter nucleus will have 96 protons. The number of nucleons (protons + neutrons) remains the same during alpha decay. Therefore, the daughter nucleus will also have 245 neutrons, which is the same as the original atom.

The correct answer is that the mass of an atom is concentrated in the nucleus. The nucleus of an atom contains the protons and neutrons, which have much greater mass compared to the electrons. The electrons, on the other hand, have negligible mass in comparison to the protons and neutrons. Therefore, the majority of the mass of an atom is concentrated in the nucleus.

A gamma ray is a high-energy electromagnetic radiation that is often emitted during radioactive decay or nuclear reactions. It is not an electron, positron, or a helium nucleus, which are all particles with mass. Instead, a gamma ray is a type of photon, which is a particle of light that has no mass.

The neutron number (N) of an atom is equal to the atomic mass (A) minus the atomic number (Z). This is because the atomic mass represents the total number of protons and neutrons in the nucleus of an atom, while the atomic number represents the number of protons. Therefore, subtracting the atomic number from the atomic mass gives the number of neutrons.

The correct answer is 6 because carbon-14 is an isotope of carbon, which means it has 6 protons in its nucleus. The number 14 in carbon-14 represents the total number of protons and neutrons in the nucleus, so there are also 8 neutrons present. However, the question specifically asks for the number of protons, which is 6 in this case.

A γ-ray is a high-energy electromagnetic wave, similar to X-rays and light, but with much higher energy. It is produced during radioactive decay or nuclear reactions. Since it is an electromagnetic wave, it is composed of photons. Therefore, the correct answer is "a photon."

Gamma rays are a form of electromagnetic radiation with high energy and short wavelength. They have the ability to penetrate various materials due to their high energy. While they can easily pass through air and a piece of paper, they require thicker barriers to be absorbed or stopped. Several centimeters of lead, being a dense material, is capable of effectively blocking gamma rays. Therefore, it is the correct answer as it provides a sufficient barrier for gamma ray absorption.

The atomic number of an element represents the number of protons in its nucleus. In this question, the element has an atomic number of 6, which means it has 6 protons. Therefore, the correct answer is 6.

The correct answer is the limited range of the strong nuclear force. The strong nuclear force is responsible for holding the nucleus of an atom together. However, this force only acts over a very short range, which means that as the size of the nucleus increases, the force becomes weaker and unable to overcome the repulsive electrostatic forces between the positively charged protons. This ultimately limits the size of a stable nucleus. The electrostatic force and gravitational force are not directly related to the stability of a nucleus.

A ß+ particle is also known as a positron. This is because a positron is a subatomic particle with the same mass as an electron but with a positive charge. It is the antimatter counterpart of an electron, meaning that it has the opposite charge. When a positron collides with an electron, they annihilate each other, releasing energy in the form of gamma rays. Positrons are commonly used in medical imaging techniques such as positron emission tomography (PET) scans.

An atom's atomic number is determined by the number of protons in its nucleus. The atomic number represents the number of protons in an atom, which determines its identity as a specific element. Neutrons, nucleons, and alpha particles are not used to determine the atomic number of an atom.

The correct answer is mass defect. The binding energy of a nucleus is contributed to by the mass defect, which is the difference between the mass of the individual nucleons (protons and neutrons) and the mass of the nucleus as a whole. This mass difference is converted into energy according to Einstein's mass-energy equivalence principle (E=mc^2). The greater the mass defect, the greater the binding energy of the nucleus. Therefore, the mass defect plays a crucial role in determining the stability and energy release in nuclear reactions.

Beta rays are high-energy electrons or positrons that can penetrate certain materials. They have a moderate penetrating power and can pass through air and thin materials like paper easily. However, they are stopped or absorbed by denser materials like aluminum and lead. Several millimeters of aluminum is enough to block or attenuate beta rays, making it an effective shield against them.

An α particle is commonly known as a helium nucleus. It consists of two protons and two neutrons, making it identical to the nucleus of a helium atom. It is called an α particle because it is emitted during certain types of radioactive decay, such as alpha decay. It has a positive charge and is relatively large compared to other subatomic particles like electrons or photons.

The atomic number of an element represents the number of protons in the nucleus of an atom. Since the atomic number of calcium is 20, it means that there are 20 protons in one atom of calcium. In a neutral atom, the number of electrons is equal to the number of protons. Therefore, there are 20 electrons in one atom of calcium.

When an alpha particle is emitted from an unstable nucleus, it consists of two protons and two neutrons. Since the alpha particle is being emitted, it means that the nucleus is losing these particles. As protons determine the atomic number of an element, losing two protons means that the atomic number decreases by 2. Therefore, the correct answer is "decreases by 2".

The atomic number of an element represents the number of protons in its nucleus. In this case, the atomic number of calcium 39 is given as 20. Therefore, there are 20 protons in one atom of calcium 39.

When a gamma ray is emitted from an unstable nucleus, there is no change in either the number of neutrons or the number of protons. Gamma rays are high-energy photons that are emitted during a nuclear decay process. Unlike alpha and beta particles, gamma rays do not carry any charge or mass, so they do not affect the number of neutrons or protons in the nucleus. Therefore, the number of neutrons and protons remains the same before and after the emission of a gamma ray.

The mass number of an atom is determined by the number of nucleons in its nucleus. Nucleons include both protons and neutrons. The protons determine the atomic number of the atom, while the neutrons contribute to the mass number. Therefore, the correct answer is nucleons in its nucleus.

An α-particle is not an electron, positron, helium nucleus, or a photon. An α-particle is actually a helium nucleus, consisting of two protons and two neutrons. Therefore, the correct answer is "a helium nucleus".

Alpha particles have an atomic mass equal to 4. Alpha particles are made up of two protons and two neutrons, giving them a total of four atomic mass units. This makes them heavier than a single proton or neutron, which have an atomic mass of 1. Alpha particles are commonly emitted during radioactive decay processes, such as in the decay of uranium or radon.

The atomic mass unit is defined as one twelfth the mass of a carbon-12 atom. This means that the mass of one atomic mass unit is equal to 1/12th of the mass of a carbon-12 atom. This unit is used to express the relative masses of atoms and molecules. By defining it in terms of a specific isotope of carbon, it allows for consistent and accurate measurements of atomic masses.

An alpha particle is a positively charged particle consisting of two protons and two neutrons. According to the principles of electrostatics, opposite charges attract each other. Therefore, an alpha particle, being positively charged, will be attracted to a negative charge.

When a neutron is emitted from an unstable nucleus, it means that one neutron is being lost from the nucleus. Since the atomic mass number is the sum of the protons and neutrons in the nucleus, losing a neutron would result in a decrease in the atomic mass number by 1. Therefore, the correct answer is "decreases by 1".

When nucleons join to form a stable nucleus, energy is released. This is because the process of nucleons coming together to form a nucleus involves the strong nuclear force, which is a very powerful force of attraction. As the nucleons come closer together and overcome the repulsive electromagnetic forces between them, energy is released in the form of binding energy. This binding energy is what holds the nucleus together and is released during the formation process. Hence, the correct answer is released.

The atomic number of an element represents the number of protons in its nucleus, while the mass number represents the total number of protons and neutrons. To find the number of neutrons in one atom of calcium with a mass number of 39, we subtract the atomic number (20) from the mass number (39). Therefore, there are 19 neutrons in one atom of calcium 39.

The nuclear force is not weak and much smaller in relative magnitude compared to the electrostatic and gravitational forces. The nuclear force is actually very strong and acts over very short distances, which makes it much stronger than both the electrostatic and gravitational forces.

The alpha particle has the most mass compared to the other particles listed (beta, electron, and gamma). An alpha particle consists of two protons and two neutrons, which gives it a mass of approximately four atomic mass units (AMU). In comparison, a beta particle (an electron or a positron) has a mass of only about 1/1836 AMU, and an electron and gamma particle have negligible mass. Therefore, the alpha particle has the most mass among these options.

Gamma rays are a type of electromagnetic radiation with high energy and short wavelength. Visible light is also a type of electromagnetic radiation, but with lower energy and longer wavelength compared to gamma rays. Both gamma rays and visible light are part of the electromagnetic spectrum, but they differ in terms of energy and wavelength. Therefore, visible light is the option that is most nearly the same as a gamma ray.

The half-life of a radioactive substance refers to the time it takes for half of the substance to decay. As the substance continues to decay, the amount of radioactive material decreases, but the half-life remains constant. This means that regardless of how much of the substance is left, it will always take the same amount of time for half of it to decay. Therefore, the correct answer is that the half-life of a radioactive substance remains constant.

Alpha decay occurs when an atomic nucleus emits an alpha particle, which consists of two protons and two neutrons. This causes the atomic number of the element to decrease by 2, as two protons are lost. Therefore, if an element with atomic number 88 undergoes alpha decay, its atomic number will become 86.

After each half-life, the amount of radioactive material is reduced by half. Since the half-life of the radioactive sample is 10 minutes, after 40 minutes, there would be 4 half-lives. Therefore, the fraction of the sample left would be (1/2)^(4) = 1/16.

In beta decay, an electron is emitted. This process occurs when a neutron in the nucleus of an atom transforms into a proton, and in order to maintain charge balance, an electron is emitted. This electron is known as a beta particle and carries a negative charge. Beta decay is a type of radioactive decay and is commonly observed in isotopes with an excess of neutrons.

During β- decay, a neutron is transformed into a proton. This process occurs when a neutron in the nucleus of an atom decays into a proton, releasing an electron and an antineutrino. This decay is accompanied by the conversion of one of the down quarks within the neutron into an up quark, resulting in a change in charge from zero (neutron) to +1 (proton). This transformation is a fundamental process in nuclear physics and is responsible for the stability of atomic nuclei.

When an element undergoes β- decay, one of its neutrons is converted into a proton, resulting in an increase in atomic number by one. Since the element in question has an atomic number of 6 before decay, it means it has 6 protons and 6 neutrons. After β- decay, one neutron is converted into a proton, resulting in 7 protons. Therefore, the atomic number of the element is now 7.

The half-life of a substance is the amount of time it takes for half of the substance to decay. In this case, the half-life is 2.3 years. After 2.3 years, half of the atoms will decay, leaving 2.0 x 10^18 atoms remaining. After another 2.3 years (a total of 4.6 years), half of the remaining atoms will decay again, leaving 1.0 x 10^18 atoms remaining. Since 3.7 years is less than 4.6 years, there will be more than 1.0 x 10^18 atoms remaining. Therefore, the correct answer is 1.3 x 10^18 atoms.

The nuclear force between adjacent protons in a nucleus is much larger compared to the electrostatic force. This is because the nuclear force is responsible for holding the protons together in the nucleus, overcoming the electrostatic repulsion between positively charged protons. The nuclear force is a short-range force that acts only within the nucleus, while the electrostatic force acts over longer distances. Therefore, the nuclear force is much stronger than the electrostatic force in this context.

The atomic number of an element represents the number of protons in its nucleus, while the mass number represents the sum of protons and neutrons. In this case, the atomic number of calcium is 20, indicating that it has 20 protons. The mass number is 39, which means that the nucleus of calcium-39 contains 20 protons and 19 neutrons. Since both protons and neutrons are nucleons, the total number of nucleons in one atom of calcium-39 is 39.

The hydrogen nucleus consists of a single proton. This is because hydrogen is the simplest element with atomic number 1, meaning it has one proton in its nucleus. It does not have any neutrons in its nucleus, as hydrogen-1 is the most common and stable isotope of hydrogen. Therefore, the correct answer is a single proton.

When a ß+ particle (also known as a positron) is emitted from an unstable nucleus, it means that a proton is being converted into a neutron. Since a proton has an atomic number of 1 and a neutron has an atomic number of 0, the atomic number of the nucleus decreases by 1 when a ß+ particle is emitted.

The existence of the neutrino was postulated in order to explain beta decay. Beta decay is a radioactive decay process in which a nucleus emits a beta particle (either an electron or a positron) and transforms into a different element. However, according to the law of conservation of energy and momentum, the energy and momentum of the emitted beta particle did not add up in experiments. To resolve this discrepancy, Wolfgang Pauli proposed the existence of a neutral and nearly massless particle, which he called the neutrino. The neutrino carries away the missing energy and momentum in beta decay, making the conservation laws valid.

The activity of a radioactive substance decreases by half every half-life. Since the half-life of the substance is 3.0 days, after 3.0 days the activity would be 0.12 Ci. After another 3.0 days (a total of 6.0 days), the activity would decrease by half again, resulting in an activity of 0.06 Ci. Therefore, the correct answer is 0.06 Ci.

Alpha rays are made up of positively charged particles called alpha particles, which are relatively large and heavy. Due to their size and charge, alpha particles interact strongly with matter and are easily absorbed. They can be stopped by a sheet of paper because the particles collide with the atoms in the paper, losing energy and eventually coming to a stop. However, they can penetrate air because the density of air is much lower than that of a solid material like paper. Alpha rays cannot penetrate several millimeters of aluminum or several centimeters of lead because these materials are denser and have more atoms for the alpha particles to interact with, resulting in greater absorption.

The activity of a radioactive substance is directly proportional to the number of radioactive nuclei present. The half-life of a radioactive substance is the time it takes for half of the radioactive nuclei to decay. In this case, the half-life of iodine-137 is 8.0 days. To find the number of iodine nuclei necessary to produce an activity of 1.0 micro Ci, we can use the equation for radioactive decay:

Activity = Initial activity * (1/2)^(t/half-life)

where t is the time and half-life is the half-life of the substance. Rearranging the equation, we can solve for the initial activity:

Initial activity = Activity * (2)^(t/half-life)

Since the initial activity is 1.0 micro Ci and the half-life is 8.0 days, we can substitute these values into the equation to find the number of iodine nuclei necessary. The answer is 3.7 x 10^10.