Nuclear Chemistry Overview

Nuclear Chemistry

• Nuclear chemistry studies changes in the nucleus of an atom, unlike chemical reactions which focus on electron interactions
• Chemical reactions involve the change of one substance into another, while atoms maintain their identity
• Nuclear reactions involve the conversion of atoms of one element into atoms of another element
• Chemical reactions produce small amounts of energy, while nuclear reactions produce large amounts of energy
• Reaction rates in chemical reactions depend on factors like temperature, concentration, and catalysts, but nuclear reaction rates are unaffected by these factors, only depending on the concentration of the element undergoing the reaction

Nuclides

• A nuclide is a particular type of nucleus, distinguished by its atomic number and nucleon number
• Nucleon number (or mass number) is the total number of protons and neutrons within the nucleus

Nuclide Symbolism and Isotopes

• Nuclide symbolism represents atomic nuclei, using the notation A/ZX
• A is the mass number (nucleon number)
• Z is the atomic number
• X is the element symbol
• Isotopes are variants of the same element that differ in their neutron numbers (and hence mass number)

Nuclear Stability

• Electrostatic force attracts opposite electrical charges
• Strong force is the force between protons and neutrons
• Neutrons increase the strong force's attraction without increasing electrostatic repulsion, affecting nuclear stability

Band of Stability

• The band of stability is a graph plotting the number of neutrons against the number of protons in stable nuclides
• A one-to-one neutron-to-proton ratio is a characteristic of stability for lighter elements
• Heavier elements need more neutrons compared to protons to maintain stability

Alpha Emission

• Alpha emission involves the loss of an alpha particle (two protons and two neutrons) from the nucleus.
• The atomic number decreases by 2 and the mass number decreases by 4.
• Energy is released during this process

Beta (-) Emission

• Beta (-) emission occurs when a neutron converts into a proton emitting an electron.
• The atomic number increases by 1, and the mass number remains the same.
• Energy is released.
• An electron is ejected from the atom.

Beta (+) Emission (Positron Emission)

• A proton converts to a neutron, releasing a positron (positive electron)
• Atomic number decreases by one and the mass number remains the same
• Energy is released
• A positron is ejected from the atom

Electron Capture

• An electron combines with a proton in the nucleus, forming a neutron.
• Atomic number decreases by 1, mass number remains the same
• Energy is released

Gamma Emission

• Gamma emission is the release of high-energy electromagnetic radiation (gamma rays) from an excited nucleus
• The atomic number and mass number remain the same
• Occurs after alpha or beta decay of a nucleus that remains in an excited energy state

Properties of α, β and γ rays

• Alpha (α) rays: consist of positively charged alpha particles; relatively low velocity, high ionization, low penetration; slightly deflected by electric or magnetic fields
• Beta (β) rays: consist of negatively charged beta particles (electrons); high velocity, moderate ionization, higher penetration; strongly deflected by electric and magnetic fields
• Gamma (γ) rays: are electromagnetic radiations; highest velocity, lowest ionization, highest penetration; not deflected by electric and magnetic fields

Nuclear Reactions

• Reactions involving changes in the nucleus, rather than electron transfer
• Different isotopes of the same element can undergo different nuclear reactions

Rates and Energy In Nuclear Reactions

• Nuclear reaction rates are unaffected by factors such as temperature, pressure, or the presence of other atoms
• Nuclear reactions generally release more energy compared to chemical reactions

Half-Life

• The time it takes for half of a radioactive sample to decay.
• Radioactive decay follows a predictable exponential pattern

Radioactive Decay Series

• A series of nuclear decays that occur until a stable isotope forms
• Chart showing the transitions between unstable nuclides

Radiation Effects on the Body

• Radioactive emissions can ionize atoms and molecules in the body
• This creates free radicals (unstable molecules with unpaired electrons)
• Free radicals can react with essential biological molecules, causing damage

Uses for Radioactive Isotopes

• Cancer treatment
• Computer imaging techniques
• Radiocarbon dating
• Smoke detectors
• Food irradiation
• Radioactive tracers

Application of Radioisotopes

• Studying reaction mechanisms (e.g., photosynthesis and ester hydrolysis)
• Medical use (e.g., cancer detection and treatment)
• Agriculture (e.g., food preservation, plant mutation, fertilizer efficiency)
• Industrial applications (e.g., detecting leaks, measuring thickness)

Nuclear Equations

• Symbolic representation of nuclear processes
• Conservation of mass and charge is obeyed in all nuclear equations.

General Nuclear Equations

• Symbolic representation showing the transformations during radioactive decays

Nuclear Energy

• Energy released when a nucleus forms
• Binding energy per nucleon increases for atoms with a mass number around 56, indicating that fusing small atoms or splitting large atoms into medium-sized atoms releases energy
• Binding energy per nucleon then decreases for larger atoms.

Nuclear Fission

• The splitting of a heavy nucleus into two or more lighter nuclei
• Large amount of energy released.
• Can lead to a chain reaction.

Nuclear Fusion

• The process where two or more small nuclei combine to form a larger nucleus
• Also releases large amount of energy
• Powers the Sun

Nuclear Reactor

• Device that controls nuclear reactions to generate electricity
• Uses nuclear fission to produce heat for turning water into steam
• Control rods regulate the rate of the fission reactions

Chain Reactions (Nuclear Fission)

• Self-sustaining sequence of nuclear fission events
• Releases a great deal of energy.

This quiz covers the fundamental concepts of nuclear chemistry, including the differences between nuclear and chemical reactions, the definition of nuclides, and nuclide symbolism. Test your understanding of how atomic nuclei behave and the factors influencing nuclear reactions.