Question

Define fission and write the reaction in which \(\mathrm{a}^{235} \mathrm{U}\) nucleus is fissioned into typical products.

Short answer

Fission is the splitting of a heavy nucleus like uranium-235 into smaller nuclei, releasing energy. For uranium-235 fission: \( \ce{^{235}_{92}U + ^1_0n -> ^{141}_{56}Ba + ^{92}_{36}Kr + 3^1_0n} \).

Step-by-step solution

Understanding Fission

Fission is a nuclear reaction process in which a heavy nucleus, such as uranium-235, splits into smaller nuclei, along with neutrons and a large amount of energy. This process can occur spontaneously or be induced by the absorption of a neutron.

Identify the Reactants

In the fission of a uranium-235 nucleus, a neutron is required to start the reaction. The reactants in the fission process thus include a uranium-235 (\( \text{U} \)) nucleus and a free neutron (\( \text{n} \)).

Write the Fission Reaction

A typical fission reaction involves the absorption of a neutron by a uranium-235 nucleus, which then becomes unstable and splits into smaller nuclei known as fission products. As a common example, a uranium-235 nucleus can split to form barium-141 (\( \text{Ba} \)) and krypton-92 (\( \text{Kr} \)), along with the release of additional neutrons and energy.

Balance the Fission Equation

Write the balanced nuclear reaction equation:\[ \ce{^{235}_{92}U + ^1_0n -> ^{141}_{56}Ba + ^{92}_{36}Kr + 3^1_0n} \]In this fission reaction, the sum of the atomic numbers and the mass numbers are balanced on both sides of the equation.

Key concepts

uranium-235

Uranium-235, often denoted as \(^{235}_{92}U\), is a specific isotope of the element uranium. It is a vital element in the process of nuclear fission, especially in nuclear reactors and atomic bombs. Uranium-235 is unique because it is capable of sustaining a chain reaction of nuclear fission.

Each atom of uranium-235 consists of 92 protons and 143 neutrons, giving it a combined mass number of 235. Its ability to undergo fission makes it a critical component for generating electricity in nuclear power plants. Interestingly, only about 0.7% of natural uranium is uranium-235, with the rest mostly being uranium-238.
When a uranium-235 nucleus absorbs a neutron, it becomes unstable, often resulting in a nuclear fission event, releasing a substantial amount of energy.

nuclear reactions

Nuclear reactions involve changes in an atom’s nucleus and typically lead to the transformation of elements. Unlike chemical reactions that involve electrons in atoms, nuclear reactions change the atom's nucleus.
A common nuclear reaction is fission, where a large nucleus splits into smaller nuclei. This process releases energy and more neutrons that can continue the reaction.
Fission reactions begin when a neutron collides with a nucleus, causing it to become unstable. This instability leads to the nucleus splitting into two or more smaller nuclei, known as fission products, along with additional neutrons. The energy released in this process is substantial, which is why it's used in nuclear power plants to generate electricity.
One important aspect of handling nuclear reactions is controlling them to prevent excessive energy release and potential hazards.

fission products

Fission products are the fragments that result from the splitting of a heavy nucleus such as uranium-235. These are smaller nuclei that contain less mass than the original uranium-235 nucleus.
When uranium-235 undergoes fission, it typically breaks into two main fragments. Common fission products in this type of reaction include barium-141 (\(^{141}_{56}Ba\) and krypton-92 (\(^{92}_{36}Kr\). Other fission products are neutrons, which further sustain the fission process.
These products are radioactive and may undergo further decay, resulting in various isotopes of different elements. The fission process does not always produce the same products; the resultant fission products can vary with each reaction. Understanding these products is crucial for managing nuclear waste and understanding the nuclear fission process in reactors.

nuclear equation balancing

Balancing nuclear equations is essential to accurately represent nuclear reactions like fission. To balance a nuclear equation, one must ensure that the atomic numbers and mass numbers on both sides of the equation are equal.
In the fission of uranium-235, for example, the equation \( \ce{^{235}_{92}U + ^1_0n -> ^{141}_{56}Ba + ^{92}_{36}Kr + 3^1_0n} \) must be balanced.
The mass numbers on both sides should add up to the same TOTAL value, in this case 236. So, \(235\) from uranium combines with \(1\) from the neutron equals \(236\).
These are balanced on the other side by \(141\) from barium plus \(92\) from krypton, and adding one for each of the three neutrons totals \(236\), achieving balance. Similarly, atomic numbers must also balance:
\(92\) from uranium becomes \(56\) from barium plus \(36\) from krypton, consistently resulting in the same sum of \(92\).