Let's break down your question about uranium-235 (U-235) and its alpha activity, as well as the concepts of half-life and disintegration probability. Understanding these concepts will help clarify the behavior of radioactive materials like U-235.

What Does Alpha Active Mean?

When we say that a substance is "alpha active," we mean that it undergoes alpha decay. In this process, the nucleus of an atom emits an alpha particle, which consists of two protons and two neutrons (essentially a helium nucleus). This emission reduces the atomic number of the original atom by two and the mass number by four, transforming it into a different element. For U-235, this means that when it decays, it can turn into thorium-231 or other isotopes, depending on the decay chain.

Understanding Half-Life

The half-life of a radioactive isotope is the time it takes for half of a sample of that isotope to decay. For U-235, the half-life is about 703.8 million years. This means that if you start with a certain amount of U-235, after 703.8 million years, half of it will have decayed into other elements.

Probability of Disintegration

Now, let's address the statements regarding the probability of a nucleus disintegrating:

• (a) The probability of a nucleus disintegrating during one second is lower in the first half-life and greater in the fifth half-life.
• (b) The probability of a nucleus disintegrating during one second remains constant for all time.
• (c) Quite an appreciable quantity of U-235 will remain even after the average life.
• (d) The energy of the emitted alpha particle is less than the disintegration energy of the U-235 nucleus.

Analyzing Each Statement

Let's evaluate each statement based on our understanding of radioactive decay:

Statement (a)

This statement is incorrect. The probability of disintegration for a given nucleus remains constant over time. This is a fundamental property of radioactive decay, described by the decay constant. The number of disintegrations per second does decrease as the amount of U-235 decreases, but the probability for any individual nucleus does not change.

Statement (b)

This statement is correct. The probability of a nucleus disintegrating in a given time interval is constant. This means that if you have a large quantity of U-235, the likelihood of any single nucleus decaying remains the same regardless of how long it has been since the sample was formed.

Statement (c)

This statement is also correct. Even after several half-lives, a significant amount of U-235 will still be present. For example, after five half-lives, only about 3.125% of the original amount remains, which is still appreciable in practical terms.

Statement (d)

This statement is generally true. The energy of the emitted alpha particle is indeed less than the disintegration energy of the U-235 nucleus. The disintegration energy refers to the energy required to break the nucleus apart, while the alpha particle carries away some of that energy during the decay process.

Conclusion

In summary, U-235 is alpha active, meaning it undergoes alpha decay. The probability of disintegration for any individual nucleus remains constant over time, and a significant amount of U-235 will still be present even after many half-lives. Understanding these principles is crucial for studying radioactive materials and their applications in fields like nuclear energy and medicine.

Let's break down your question about Uranium-235 (U-235) and its alpha activity. First, it's important to understand what it means for a substance to be "alpha active." This term refers to the type of radioactive decay that occurs when an unstable nucleus emits an alpha particle, which consists of two protons and two neutrons. This process reduces the atomic number of the element by two, effectively transforming it into a different element. In the case of U-235, when it undergoes alpha decay, it becomes Thorium-231 (Th-231).

Understanding Half-Life and Decay Probability

Now, let’s discuss the concept of half-life. The half-life of a radioactive isotope is the time required for half of the radioactive nuclei in a sample to decay. For U-235, this half-life is about 703.8 million years. This means that if you start with a certain amount of U-235, after one half-life, half of that amount will have decayed into Th-231, and the other half will still be U-235.

Analyzing the Options

Now, let’s evaluate the statements you provided regarding the behavior of U-235 over time:

• (a) The probability of a nucleus disintegrating during one second is lower in the first half-life and greater in the fifth half-life.
• (b) The probability of a nucleus disintegrating during one second remains constant for all time.
• (c) Quite an appreciable quantity of U-235 will remain even after the average life.
• (d) The energy of emitted alpha particles is less than the disintegration energy of the U-235 nucleus.

Evaluating Each Statement

Let’s go through each statement one by one:

Statement (a)

This statement is incorrect. The probability of decay for a single nucleus is constant over time. This means that the likelihood of a nucleus disintegrating in any given second does not change as time progresses. The decay process is random, but the overall decay rate is constant.

Statement (b)

This statement is correct. The probability of a nucleus disintegrating during any given second remains constant throughout its existence. This is a fundamental principle of radioactive decay, known as the constant decay rate.

Statement (c)

This statement is also correct. Even after a significant amount of time, a measurable quantity of U-235 will remain. Since the half-life is so long, it takes billions of years for a substantial amount of U-235 to decay. Therefore, even after several half-lives, some U-235 will still be present.

Statement (d)

This statement is generally incorrect. The energy of the emitted alpha particles is typically a significant fraction of the disintegration energy of the U-235 nucleus. In fact, the alpha decay process releases energy, which is why it occurs spontaneously. The energy of the emitted alpha particle is usually less than the binding energy of the nucleus, but it is not less than the disintegration energy itself.

Summary of Findings

To summarize, the correct statements regarding U-235 are (b) and (c). The probability of decay remains constant over time, and a considerable amount of U-235 will still exist even after many half-lives. Understanding these principles is crucial for grasping the behavior of radioactive materials and their applications in fields like nuclear energy and medicine.

If you have any further questions or need clarification on any of these points, feel free to ask!

Let's break down your question about uranium-235 (U-235) and its alpha activity, as well as the concepts of half-life and radioactive decay. Understanding these concepts will help clarify the statements you've presented.

What Does Alpha Active Mean?

When we say that a substance is "alpha active," we mean that it undergoes alpha decay. In this process, the nucleus of an atom emits an alpha particle, which consists of two protons and two neutrons (essentially a helium nucleus). This type of decay reduces the atomic number of the original element by two and the mass number by four, transforming the element into a different one. For U-235, alpha decay is one of the primary ways it loses energy and transforms into a more stable isotope.

Understanding Half-Life

The half-life of a radioactive substance is the time it takes for half of the radioactive nuclei in a sample to decay. For U-235, the half-life is about 703.8 million years. This means that if you start with a certain amount of U-235, after one half-life, half of that amount will have decayed into other elements, and this process continues over successive half-lives.

Analyzing the Statements

• (a) The probability of a nucleus disintegrating during one second is lower in the first half-life and greater in the fifth half-life.
• (b) The probability of a nucleus disintegrating during one second remains constant for all time.
• (c) Quite an appreciable quantity of U-235 will remain even after the average life.
• (d) The energy of the emitted alpha particle is less than the disintegration energy of the U-235 nucleus.

Evaluating Each Statement

Let's go through each statement to determine its validity:

Statement (a)

This statement is incorrect. The probability of a nucleus disintegrating is constant over time, meaning it does not change between the first and fifth half-lives. The decay process is random, and while the amount of U-235 decreases over time, the probability of any single nucleus decaying in a given second remains the same throughout its lifetime.

Statement (b)

This statement is correct. The probability of a nucleus disintegrating per unit time is constant, which is a fundamental characteristic of radioactive decay. This constancy is what allows us to use the concept of half-life effectively.

Statement (c)

This statement is also correct. Even after several half-lives, a significant amount of U-235 will still remain. For example, after five half-lives, only about 3.125% of the original amount will have decayed, meaning a considerable quantity is still present.

Statement (d)

This statement is generally true. The energy of the emitted alpha particle is indeed less than the disintegration energy of the U-235 nucleus. The disintegration energy refers to the energy required to break apart the nucleus, while the energy of the emitted alpha particle is the energy released during the decay process, which is lower than the total energy holding the nucleus together.

Conclusion

In summary, U-235 is alpha active, meaning it undergoes alpha decay. The probability of decay remains constant over time, and even after several half-lives, a notable amount of U-235 will still exist. Understanding these principles helps us grasp the nature of radioactive decay and the behavior of isotopes like U-235 in various applications, including nuclear energy and radiometric dating.

Let's delve into the concept of alpha activity and the behavior of Uranium-235 (U-235) in terms of its radioactive decay. When we say that U-235 is "alpha active," we mean that it undergoes alpha decay, a type of radioactive decay where an alpha particle (which consists of 2 protons and 2 neutrons) is emitted from the nucleus of the atom. This process transforms the original nucleus into a different element, in this case, Thorium-231, while also releasing energy.

Understanding Radioactive Decay

Radioactive decay is a random process at the level of individual nuclei, but it can be described statistically for a large number of atoms. Each type of radioactive isotope has a characteristic half-life, which is the time it takes for half of a sample of that isotope to decay. For U-235, the half-life is about 703.8 million years.

Analyzing the Statements

Now, let's break down the statements you provided regarding U-235:

• (a) The probability of a nucleus disintegrating during one second is lower in the first half-life and greater in the fifth half-life.
• (b) The probability of a nucleus disintegrating during one second remains constant for all time.
• (c) Quite an appreciable quantity of U-235 will remain even after the average life.
• (d) The energy of emitted alpha particles is less than the disintegration energy of the U-235 nucleus.

Evaluating Each Statement

Let's evaluate each statement based on our understanding of radioactive decay:

Statement (a)

This statement is incorrect. The probability of decay for a single nucleus is constant over time. It does not change based on how long the nucleus has existed. The decay process is random, and while the number of undecayed nuclei decreases over time, the probability of any individual nucleus decaying remains the same.

Statement (b)

This statement is correct. The probability of a nucleus disintegrating during any given second is constant. This is a fundamental property of radioactive decay, described by the exponential decay law. The decay rate is independent of the amount of substance present.

Statement (c)

This statement is also correct. Even after several half-lives, a significant amount of U-235 will still remain. For example, after one half-life, 50% of the original amount remains; after two half-lives, 25% remains; after three, 12.5%, and so on. It takes many half-lives for the quantity to become negligible.

Statement (d)

This statement is generally incorrect. The energy of the emitted alpha particles is typically less than the binding energy of the nucleus, but it is not necessarily less than the disintegration energy of the U-235 nucleus. The emitted alpha particle carries away energy, but the total energy involved in the decay process can be complex and depends on various factors, including the specific decay path and the energy levels of the involved nuclei.

Conclusion

In summary, U-235 is alpha active, meaning it undergoes alpha decay. The probability of decay remains constant over time, and a significant amount of U-235 will still be present even after many half-lives. Understanding these principles is crucial for grasping the behavior of radioactive materials and their applications in fields like nuclear energy and medicine.

Let's delve into your question about Uranium-235 (U-235) and its alpha activity. To start, when we say that U-235 is "alpha active," we mean that it undergoes alpha decay, a type of radioactive decay where an unstable nucleus emits an alpha particle. An alpha particle consists of two protons and two neutrons, essentially a helium nucleus. This process reduces the atomic number of the original nucleus, leading to the formation of a different element, in this case, Thorium-231.

Understanding the Concepts

Now, let’s break down the statements you provided regarding the behavior of U-235 over time:

Statement Analysis

• (a) The probability of a nucleus disintegrating during one second is lower in the first half-life and greater in the fifth half-life.
• (b) The probability of a nucleus disintegrating during one second remains constant for all time.
• (c) Quite an appreciable quantity of U-235 will remain even after the average life.
• (d) The energy of emitted alpha particles is less than the disintegration energy of the U-235 nucleus.

Evaluating Each Statement

Let’s evaluate each of these statements one by one:

Statement (a)

This statement is incorrect. The probability of a nucleus disintegrating is constant over time, which means it does not change from the first half-life to the fifth half-life. This is a fundamental property of radioactive decay, where the decay constant remains the same regardless of how much time has passed.

Statement (b)

This statement is correct. The probability of a nucleus disintegrating per unit time (or per second) is constant. This is because radioactive decay follows an exponential decay law, meaning that the rate of decay is proportional to the number of undecayed nuclei present at any given time.

Statement (c)

This statement is also true. Even after several half-lives, a significant amount of U-235 will still remain. For example, after one half-life, 50% of the original quantity remains; after two half-lives, 25% remains; and so on. It takes an infinite amount of time for a radioactive substance to decay completely, so a measurable amount will always be present.

Statement (d)

This statement is generally true. The energy of the emitted alpha particles is indeed less than the disintegration energy of the U-235 nucleus. The disintegration energy refers to the total energy required to break the nucleus apart, while the energy of the emitted alpha particle is a fraction of that energy, as some energy is released in the form of kinetic energy of the remaining nucleus and other particles.

Conclusion

In summary, U-235 is alpha active, meaning it undergoes alpha decay. The probability of decay remains constant over time, and while a significant amount of U-235 will remain even after many half-lives, the energy of the emitted alpha particles is less than the disintegration energy of the nucleus. This understanding of radioactive decay is crucial in fields like nuclear physics and radiochemistry.

If you have any further questions or need clarification on any of these points, feel free to ask!