Nuclear Reactions — Transforming the Atom's Core
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Nuclear reactions involve changes to an atom's nucleus — fundamentally different from chemical reactions, which only rearrange electrons. Nuclear reactions convert one element into another (transmutation), release or absorb enormous amounts of energy, and involve particles like alpha particles, beta particles, neutrons, and gamma rays. The energy involved in nuclear reactions is millions of times greater per atom than in chemical reactions, governed by Einstein's mass-energy equivalence E = mc2.
Reaction Mechanism
Nuclear fission splits heavy nuclei (uranium-235, plutonium-239) into lighter fragments when struck by a neutron, releasing 2-3 additional neutrons that can trigger a chain reaction. Each fission event releases about 200 MeV of energy — roughly 50 million times more than burning one molecule of octane. Nuclear fusion combines light nuclei (hydrogen isotopes deuterium and tritium) into helium, releasing even more energy per unit mass. Radioactive decay is spontaneous nuclear transformation — alpha decay reduces atomic number by 2, beta decay converts a neutron to a proton (or vice versa).
Everyday Examples
Smoke detectors use americium-241 alpha decay. Carbon-14 dating measures the radioactive decay of carbon-14 in organic materials to determine age — reliable up to about 50,000 years. Medical PET scans use positron-emitting isotopes (fluorine-18) to image metabolic activity in the body. Bananas contain potassium-40, a naturally radioactive isotope.
Industrielle Bedeutung
Nuclear power generates approximately 10 percent of global electricity from about 440 reactors in 32 countries, producing minimal CO2 during operation. Nuclear medicine uses over 40 million procedures annually for diagnosis and treatment. Industrial radiography uses gamma sources to inspect welds in pipelines and aircraft. Research reactors produce medical isotopes like technetium-99m, used in 80 percent of nuclear medicine procedures.
Safety Note
Radioactive materials require specialized shielding, monitoring, and handling protocols. Alpha particles are stopped by paper but lethal if ingested. Beta and gamma radiation require denser shielding. Follow ALARA (As Low As Reasonably Achievable) principles for radiation exposure. Nuclear waste disposal remains a major environmental and engineering challenge.
Electron Capture by Beryllium-7
⁷Be + e⁻ → ⁷Li + νₑ
Beryllium-7 captures an inner orbital electron, converting a proton to a neutron and producing lithium-7 and a neutrino. This electron …
Alpha Decay of Radium-226
²²⁶Ra → ²²²Rn + ⁴He
Radium-226 emits an alpha particle to form radon-222 gas. Radium was discovered by Marie and Pierre Curie in 1898 and …
Alpha Decay of Radon-222
²²²Rn → ²¹⁸Po + ⁴He
Radon-222, a radioactive noble gas, alpha decays to polonium-218 with a half-life of 3.82 days. As the densest naturally occurring …
Alpha Decay of Thorium-232
²³²Th → ²²⁸Ra + ⁴He
Thorium-232 alpha decays to radium-228 with a half-life of 14.05 billion years, longer than the age of the universe. Thorium …
Neutron Capture by Uranium-238
²³⁸U + ¹n → ²³⁹U → ²³⁹Np → ²³⁹Pu
Uranium-238 captures a neutron to form uranium-239, which beta decays (23.5 min) to neptunium-239, which beta decays (2.36 days) to …
Beta Decay of Iodine-131
¹³¹I → ¹³¹Xe + e⁻ + ν̄ₑ + γ
Iodine-131 beta decays to xenon-131 with a half-life of 8.02 days, also emitting gamma radiation. I-131 concentrates in the thyroid …
Beta Decay of Strontium-90
⁹⁰Sr → ⁹⁰Y + e⁻ + ν̄ₑ
Strontium-90 undergoes beta decay to yttrium-90 with a half-life of 28.8 years. Sr-90 is a major fission product and is …
Alpha Decay of Polonium-210
²¹⁰Po → ²⁰⁶Pb + ⁴He
Polonium-210 alpha decays to stable lead-206 with a half-life of 138 days. Po-210 emits a 5.3 MeV alpha particle and …
Americium-241 Alpha Decay
²⁴¹Am → ²³⁷Np + ⁴He
Americium-241 alpha decays to neptunium-237 with a half-life of 432 years, also emitting a 59.5 keV gamma ray. Am-241 is …
Beta Decay of Cobalt-60
⁶⁰Co → ⁶⁰Ni + e⁻ + ν̄ₑ + γ
Cobalt-60 beta decays to nickel-60 with emission of two gamma rays (1.17 and 1.33 MeV) and an electron. The 5.27-year …
Plutonium-239 Fission
²³⁹Pu + ¹n → ¹³⁴Xe + ¹⁰³Zr + 3¹n
Plutonium-239 undergoes neutron-induced fission similar to U-235 but with slightly higher energy release. Pu-239 is produced in reactors when U-238 …
Proton-Proton Chain (Solar Fusion)
4¹H → ⁴He + 2e⁺ + 2νₑ + energy
The proton-proton chain converts four hydrogen nuclei into one helium-4 nucleus, two positrons, and two electron neutrinos in a multi-step …
Uranium-235 Fission
²³⁵U + ¹n → ¹⁴¹Ba + ⁹²Kr + 3¹n
A uranium-235 nucleus absorbs a slow neutron and splits into barium-141 and krypton-92, releasing three neutrons and approximately 200 MeV …
Alpha Decay of Uranium-238
²³⁸U → ²³⁴Th + ⁴He
Uranium-238 emits an alpha particle (helium-4 nucleus) to become thorium-234. This is the first step in the uranium-238 decay series, …
Beta Decay of Carbon-14
¹⁴C → ¹⁴N + e⁻ + ν̄ₑ
Carbon-14 undergoes beta-minus decay to nitrogen-14, emitting an electron and an antineutrino. C-14 has a half-life of 5,730 years and …
Beta Decay of Potassium-40
⁴⁰K → ⁴⁰Ca + e⁻ + ν̄ₑ
Potassium-40 decays to calcium-40 by beta emission (89.3%) or to argon-40 by electron capture (10.7%). With a half-life of 1.25 …
Positron Emission of Carbon-11
¹¹C → ¹¹B + e⁺ + νₑ
Carbon-11 undergoes positron emission to become boron-11 with a short half-life of 20.4 minutes. C-11 can be incorporated into virtually …
Positron Emission of Fluorine-18 (PET Scan)
¹⁸F → ¹⁸O + e⁺ + νₑ
Fluorine-18 undergoes positron emission to become oxygen-18 with a half-life of 109.8 minutes. The emitted positron annihilates with an electron, …
Technetium-99m Gamma Decay
⁹⁹ᵐTc → ⁹⁹Tc + γ
Technetium-99m (metastable) releases a 140 keV gamma ray to reach the ground state Tc-99 with a half-life of 6.01 hours. …
Deuterium-Deuterium Fusion
²H + ²H → ³He + ¹n
Two deuterium nuclei fuse to produce helium-3 and a neutron, releasing 3.27 MeV. An alternative D-D reaction produces tritium and …
Tritium Beta Decay
³H → ³He + e⁻ + ν̄ₑ
Tritium (hydrogen-3) undergoes beta decay to helium-3 with a half-life of 12.3 years, emitting a very low energy electron (max …
Beta Decay of Cesium-137
¹³⁷Cs → ¹³⁷Ba + e⁻ + ν̄ₑ + γ
Cesium-137 beta decays to barium-137m (metastable), which then emits a 662 keV gamma ray to reach stable barium-137. Cs-137 has …
Triple Alpha Process (Helium Burning)
3⁴He → ¹²C + γ
Three helium-4 nuclei fuse to form carbon-12 in stars through the triple-alpha process, which occurs above 100 million K. Two …
Deuterium-Tritium Fusion
²H + ³H → ⁴He + ¹n
Deuterium and tritium fuse at temperatures exceeding 100 million degrees to form helium-4 and a neutron, releasing 17.6 MeV of …
Rutherford's Nuclear Transmutation
¹⁴N + ⁴He → ¹⁷O + ¹H
In 1919, Ernest Rutherford achieved the first artificial nuclear transmutation by bombarding nitrogen-14 with alpha particles to produce oxygen-17 and …