how do nuclei change during these reactions

Daniel Parker

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19-03-2025

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How Do Nuclei Change During Nuclear Reactions?

Nuclear reactions involve profound changes within the atomic nucleus, altering its composition and properties. Unlike chemical reactions that rearrange electrons, nuclear reactions directly modify the protons and neutrons that make up the nucleus itself. Understanding these changes is crucial to comprehending processes like nuclear fission, fusion, and radioactive decay.

Types of Nuclear Reactions and Nuclear Changes

Several processes can alter a nucleus's composition:

1. Radioactive Decay: Unstable nuclei spontaneously transform to achieve greater stability. This often involves emitting particles or energy.

• Alpha Decay: The nucleus emits an alpha particle (two protons and two neutrons), reducing its atomic number by 2 and its mass number by 4. For example, Uranium-238 decaying into Thorium-234.

• Beta Decay: A neutron transforms into a proton, emitting a beta particle (an electron) and an antineutrino. This increases the atomic number by 1 while the mass number remains unchanged. For instance, Carbon-14 decaying into Nitrogen-14.

• Gamma Decay: An excited nucleus releases energy in the form of a gamma ray (high-energy photon). This doesn't change the number of protons or neutrons, only the nucleus's energy state.

2. Nuclear Fission: A heavy nucleus splits into two or more lighter nuclei, releasing a substantial amount of energy and often neutrons. This is the process used in nuclear power plants and atomic bombs. For example, Uranium-235 undergoing fission to produce Krypton and Barium, along with neutrons. The resulting nuclei have significantly lower mass numbers than the original uranium nucleus.

3. Nuclear Fusion: Two light nuclei combine to form a heavier nucleus, also releasing a large amount of energy. This is the process powering the sun and other stars. For example, two isotopes of hydrogen (deuterium and tritium) fusing to form helium and a neutron. The resulting helium nucleus has a higher mass number than the original hydrogen nuclei.

4. Nuclear Transmutation: This involves bombarding a nucleus with particles (protons, neutrons, alpha particles) to change its identity. This can produce isotopes not found naturally or create entirely new elements. For example, bombarding nitrogen-14 with alpha particles to produce oxygen-17 and a proton. The resulting oxygen-17 nucleus has a different atomic number and potentially a different mass number than the original nitrogen-14.

Conservation Laws in Nuclear Reactions

Several fundamental laws govern nuclear reactions:

• Conservation of Mass-Energy: The total mass-energy of the system remains constant. While mass might seem to be "lost" in some reactions (like fusion), it's converted into energy according to Einstein's famous equation, E=mc².

• Conservation of Charge: The total electric charge of the system remains constant. The sum of the atomic numbers (protons) before and after the reaction must be equal.

• Conservation of Nucleon Number (Mass Number): The total number of nucleons (protons + neutrons) remains constant. The sum of the mass numbers before and after the reaction must be equal.

Visualizing Nuclear Changes

It's helpful to visualize these changes using nuclear notation. For example, the alpha decay of Uranium-238 is written as:

²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He

Where:

• The superscript represents the mass number (protons + neutrons).
• The subscript represents the atomic number (number of protons).

Understanding how nuclei change during these reactions is critical for various applications, from energy production to medical treatments. The principles of conservation of mass-energy, charge, and nucleon number provide a framework for analyzing these fundamental transformations within the atom.