Nuclear Chemistry by Owen Borville 11.3.2025
Nuclei and nuclear reactions: Radioactivity is the spontaneous emission of particles or electromagnetic radiation. All elements above Z=83 are radioactive.
While chemical reactions involve atoms rearranged by the breaking and forming of chemical bonds, in nuclear reactions elements are converted to other elements (or isotopes).
Chemical reactions only involve electrons in atomic or molecular orbitals in the reaction. In nuclear reactions, protons, neutrons, electrons, and other subatomic particles such as alpha particles may be involved.
Chemical reactions are accompanied by absorption or release of relatively small amounts of energy. Nuclear reactions are accompanied by the absorption or release of tremendous amounts of energy.
Chemical reaction rates are influenced by temperature, pressure, concentration, and catalysts. Nuclear reaction rates are normally not affected by temperature, pressure, or catalysts.
Subatomic particles include: protons, neutrons, electrons, positrons, and alpha particles. Positrons (𝑒+) are positively charged electrons. Alpha particles (α) are high-energy helium nuclei. Beta particles (β) are high energy electrons. Gamma rays (γ) compose high-energy electromagnetic radiation.
To balance nuclear reactions, balance the total of all mass numbers and total of all atomic numbers for the products and reactants. If one number is unknown, use the other numbers to set up an equation to solve for the unknown number. Balancing nuclear equations is like the conservation of mass
∑ Sum of reactant mass numbers = ∑ Sum of product mass numbers
∑ Sum of reactant atomic numbers = ∑ Sum of product atomic numbers
Principle factor for nuclear stability is neutron-to-proton ration (n/p). There are more stable nuclei with: 2, 8, 20, 50, 82, or 126 protons or neutrons. These are also known as "magic numbers" in chemistry, or specific numbers of nucleons (protons or neutrons) that result in particularly stable atomic nuclei. Electron configurations: 2, 8, 18, and 32 are a similar concept to magic numbers. Even numbers are more stable than odd numbers. All elements with atomic number greater than 83 are radioactive. All isotopes of elements Tc and Pm are radioactive.
A graph plotting the number of neutrons versus number of protons in various isotopes shows stable nuclei are located in an area of the graph known as the Belt of Stability spanning from the lower left to the upper right of the graph. Most radioactive nuclei lie outside the belt. Above the belt of stability, the nuclei have higher neutron-to-proton ratio.
Types of Nuclear Decay:
Above the belt, isotopes decay by beta emission, a type of radioactive decay where an unstable atomic nucleus transforms to become more stable by emitting a beta particle. For example, when carbon-14 decays into nitrogen-14, a neutron in the carbon-14 nucleus transforms into a proton, and emits a beta particle.
Below the belt, isotopes decay by positron emission, where a proton transforms to a neutron and a positron is emitted (Ex. decay of K to Ar).
Electron capture is a type of radioactive decay where an unstable, proton-rich nucleus absorbs an inner orbital electron, which combines with a proton to form a neutron and release a neutrino.
Nuclear Binding Energy is a quantitative measure of nuclear stability. The nuclear binding energy is the energy required to break up a nucleus into its component protons and neutrons.
The measured mass of an atom is the combined measured mass of all protons, electrons, and neutrons, the sum of which is the calculated mass of the atom (in amu).
The mass defect is the difference between the sum of the masses of an atom's protons, neutrons, electrons and the measured atomic mass (amu).
The loss in mass in converted to energy and can be quantified with Albert Einstein's mass-energy equivalence relationship equation:
ΔE = (Δm)c^2 where:
ΔE = energy of product - energy of reactant
Δm = mass of product - mass of reactant
Nuclear binding energy per nucleon versus mass number can be plotted on a graph.
Nuclear Radioactivity: The disintegration of a radioactive nucleus often is the beginning of a radioactive decay series, which is a sequence of nuclear reactions that ultimately result in the formation of a stable isotope. The beginning radioactive isotope is called the parent and the product isotope is called the daughter.
Kinetics of Radioactive Decay:
All radioactive decay obeys first-order kinetics: ln(Nt/N0) = -kt
The half-life of the reaction is t1/2 = 0.693/k
To determine the age of a material: (Step 1) determine the rate constant using: t1/2 = 0.693/k
(Step 2) Use equation ln(Nt/N0) = -kt
Nuclear Transmutation is different than radioactive decay because transmutation is caused by the collision of two particles. Particle accelerators make it possible to synthesize the transuranium elements, which have atomic numbers greater than 92. Particles can be accelerated and caused to collide with a particular nucleus to create a reaction. Neutrons can be collided with a nucleus because of their neutral charge. Fission involves splitting a nucleus apart into smaller nuclei by a particle collision. Fusion occurs when smaller nuclei combine into larger nuclei, such as in the Sun and stars.
Cyclotron is a type of particle accelerator that uses a magnetic field to bend charged particles into a spiral path, while an electric field accelerates them.
Nuclear fission is the process in which a heavy nucleus (mass >200) divides to form smaller nuclei and one or more neutrons, along with significant energy release. The released neutrons can then cause more fission reactions, creating a chain reaction that can be used to produce electricity in a nuclear power plant.
U-235 is capable of a self-sustaining sequence of nuclear fission known as a nuclear chain reaction.
The critical mass is the minimum mass of fissionable material required to generate a self-sustaining nuclear chain reaction.
Nuclear fusion is the process of combining small nuclei into larger ones. Fusion reactions are believed to take place in the sun and stars. These reactions include combining two hydrogen nuclei (H-1 and H-2) into helium (H-3) , combining two helium nuclei into a heavier helium and also hydrogen, and combining two hydrogen nuclei into heavy hydrogen (H-2) and a beta particle.
Fusion reactions are called thermonuclear reactions because they take place at very high temperatures. Due to high temperature requirements, containment is an issue and fusion is difficult to replicate on Earth. High powered-lasers have been used to create small-scale fusion at Lawrence Livermore National Laboratory, however more research is needed before this process can be useful.
Applications of isotopes are in chemical analysis. Radioactive and stable isotopes have applications in science for molecular structure determination. By analyzing the isotopic ratios for sulfur atoms in thiosulfate and the resulting products, researchers can determine how the sulfur atoms have been rearranged or redistributed in biochemical reactions and the molecular pathways involved. The sulfur-35 isotope helps label the S atoms.
Radioactive and stable isotopes have been used in applications of medicine, in particular as tracers for diagnosis including blood flow using sodium-24, thyroid conditions using iondine-131, and brain imaging using iodine-123.
The fundamental unit of radioactivity is the curie (Ci) by Marie and Pierre Curie. 1 Ci = 3.70 x 10^10 disintegrations per second, or becquerels, the SI international standard unit of radioactivity after Henri Becquerel.
Biological effects of radiation: Rad (radiation absorbed dose) is a common unit of r the absorbed dose of radiation.
1 rad = 1 x 10^-5 J/g of tissue irradiated
The rem (roentgen equivalent for man) is determined from the number of rads:
Number of rems = number of rads x 1 RBE (relative biological effectiveness)
Nuclei and nuclear reactions: Radioactivity is the spontaneous emission of particles or electromagnetic radiation. All elements above Z=83 are radioactive.
While chemical reactions involve atoms rearranged by the breaking and forming of chemical bonds, in nuclear reactions elements are converted to other elements (or isotopes).
Chemical reactions only involve electrons in atomic or molecular orbitals in the reaction. In nuclear reactions, protons, neutrons, electrons, and other subatomic particles such as alpha particles may be involved.
Chemical reactions are accompanied by absorption or release of relatively small amounts of energy. Nuclear reactions are accompanied by the absorption or release of tremendous amounts of energy.
Chemical reaction rates are influenced by temperature, pressure, concentration, and catalysts. Nuclear reaction rates are normally not affected by temperature, pressure, or catalysts.
Subatomic particles include: protons, neutrons, electrons, positrons, and alpha particles. Positrons (𝑒+) are positively charged electrons. Alpha particles (α) are high-energy helium nuclei. Beta particles (β) are high energy electrons. Gamma rays (γ) compose high-energy electromagnetic radiation.
To balance nuclear reactions, balance the total of all mass numbers and total of all atomic numbers for the products and reactants. If one number is unknown, use the other numbers to set up an equation to solve for the unknown number. Balancing nuclear equations is like the conservation of mass
∑ Sum of reactant mass numbers = ∑ Sum of product mass numbers
∑ Sum of reactant atomic numbers = ∑ Sum of product atomic numbers
Principle factor for nuclear stability is neutron-to-proton ration (n/p). There are more stable nuclei with: 2, 8, 20, 50, 82, or 126 protons or neutrons. These are also known as "magic numbers" in chemistry, or specific numbers of nucleons (protons or neutrons) that result in particularly stable atomic nuclei. Electron configurations: 2, 8, 18, and 32 are a similar concept to magic numbers. Even numbers are more stable than odd numbers. All elements with atomic number greater than 83 are radioactive. All isotopes of elements Tc and Pm are radioactive.
A graph plotting the number of neutrons versus number of protons in various isotopes shows stable nuclei are located in an area of the graph known as the Belt of Stability spanning from the lower left to the upper right of the graph. Most radioactive nuclei lie outside the belt. Above the belt of stability, the nuclei have higher neutron-to-proton ratio.
Types of Nuclear Decay:
Above the belt, isotopes decay by beta emission, a type of radioactive decay where an unstable atomic nucleus transforms to become more stable by emitting a beta particle. For example, when carbon-14 decays into nitrogen-14, a neutron in the carbon-14 nucleus transforms into a proton, and emits a beta particle.
Below the belt, isotopes decay by positron emission, where a proton transforms to a neutron and a positron is emitted (Ex. decay of K to Ar).
Electron capture is a type of radioactive decay where an unstable, proton-rich nucleus absorbs an inner orbital electron, which combines with a proton to form a neutron and release a neutrino.
Nuclear Binding Energy is a quantitative measure of nuclear stability. The nuclear binding energy is the energy required to break up a nucleus into its component protons and neutrons.
The measured mass of an atom is the combined measured mass of all protons, electrons, and neutrons, the sum of which is the calculated mass of the atom (in amu).
The mass defect is the difference between the sum of the masses of an atom's protons, neutrons, electrons and the measured atomic mass (amu).
The loss in mass in converted to energy and can be quantified with Albert Einstein's mass-energy equivalence relationship equation:
ΔE = (Δm)c^2 where:
ΔE = energy of product - energy of reactant
Δm = mass of product - mass of reactant
Nuclear binding energy per nucleon versus mass number can be plotted on a graph.
Nuclear Radioactivity: The disintegration of a radioactive nucleus often is the beginning of a radioactive decay series, which is a sequence of nuclear reactions that ultimately result in the formation of a stable isotope. The beginning radioactive isotope is called the parent and the product isotope is called the daughter.
Kinetics of Radioactive Decay:
All radioactive decay obeys first-order kinetics: ln(Nt/N0) = -kt
The half-life of the reaction is t1/2 = 0.693/k
To determine the age of a material: (Step 1) determine the rate constant using: t1/2 = 0.693/k
(Step 2) Use equation ln(Nt/N0) = -kt
Nuclear Transmutation is different than radioactive decay because transmutation is caused by the collision of two particles. Particle accelerators make it possible to synthesize the transuranium elements, which have atomic numbers greater than 92. Particles can be accelerated and caused to collide with a particular nucleus to create a reaction. Neutrons can be collided with a nucleus because of their neutral charge. Fission involves splitting a nucleus apart into smaller nuclei by a particle collision. Fusion occurs when smaller nuclei combine into larger nuclei, such as in the Sun and stars.
Cyclotron is a type of particle accelerator that uses a magnetic field to bend charged particles into a spiral path, while an electric field accelerates them.
Nuclear fission is the process in which a heavy nucleus (mass >200) divides to form smaller nuclei and one or more neutrons, along with significant energy release. The released neutrons can then cause more fission reactions, creating a chain reaction that can be used to produce electricity in a nuclear power plant.
U-235 is capable of a self-sustaining sequence of nuclear fission known as a nuclear chain reaction.
The critical mass is the minimum mass of fissionable material required to generate a self-sustaining nuclear chain reaction.
Nuclear fusion is the process of combining small nuclei into larger ones. Fusion reactions are believed to take place in the sun and stars. These reactions include combining two hydrogen nuclei (H-1 and H-2) into helium (H-3) , combining two helium nuclei into a heavier helium and also hydrogen, and combining two hydrogen nuclei into heavy hydrogen (H-2) and a beta particle.
Fusion reactions are called thermonuclear reactions because they take place at very high temperatures. Due to high temperature requirements, containment is an issue and fusion is difficult to replicate on Earth. High powered-lasers have been used to create small-scale fusion at Lawrence Livermore National Laboratory, however more research is needed before this process can be useful.
Applications of isotopes are in chemical analysis. Radioactive and stable isotopes have applications in science for molecular structure determination. By analyzing the isotopic ratios for sulfur atoms in thiosulfate and the resulting products, researchers can determine how the sulfur atoms have been rearranged or redistributed in biochemical reactions and the molecular pathways involved. The sulfur-35 isotope helps label the S atoms.
Radioactive and stable isotopes have been used in applications of medicine, in particular as tracers for diagnosis including blood flow using sodium-24, thyroid conditions using iondine-131, and brain imaging using iodine-123.
The fundamental unit of radioactivity is the curie (Ci) by Marie and Pierre Curie. 1 Ci = 3.70 x 10^10 disintegrations per second, or becquerels, the SI international standard unit of radioactivity after Henri Becquerel.
Biological effects of radiation: Rad (radiation absorbed dose) is a common unit of r the absorbed dose of radiation.
1 rad = 1 x 10^-5 J/g of tissue irradiated
The rem (roentgen equivalent for man) is determined from the number of rads:
Number of rems = number of rads x 1 RBE (relative biological effectiveness)
