Week 1: Lecture 1 Flashcards
Fundamentals of Nuclear Science: The Atomic Model
Define molecules.
Molecules are the smallest unit of a substance that exhibits its chemical properties. They consist of atoms of the same, or different elements, joined together by electrostatic forces and by sharing electrons through covalent bonds.
Define covalent bonds.
Covalent bonds are a chemical bond, which involves the sharing of electron pairs between atoms.
What is the atomic number?
The atomic number is the number of protons present in the atom, and tells us to which element the atom belongs. (Usually the bottom number in an atomic symbol).
What is the mass number?
The mass number is the sum of neutrons and protons in the nucleus. (Usually the top number in an atomic symbol).
What is an Isotope?
Isotopes are atoms with a different number of neutrons. They have a different mass, but chemically behave the same.
How is a nuclide chart plotted?
In a nuclide chart, all nuclides are plotted as a function of their number of protons and neutrons. (112 elements, ~3000 nuclides; Proton number (Z) on the y-axis; Neutron number (N) on the x-axis).
What is an Isobar?
Isobars are all nuclides with a certain mass number (Protons + Neutrons), but a different atomic number.
What is an Isotone?
Isotones are all nuclides with a certain neutron number, but a different atomic number (# of protons).
What is the mass defect?
The mass defect is the difference between the mass of a composite particle (i.e. atom) and the sum of the masses of its parts (i.e. proton, neutron, and electrons). The missing mass comes from the binding energy.
How is the atomic mass unit defined?
The atomic mass unit (u) is defined as being one twelfth of the mass of a Carbon-12 atom.
What is the binding energy?
The binding energy is the energy required to pull each particle apart from the nucleus. The binding energy per nucleon is not the same in each nuclide.
Why is the strength of the binding energy important?
The most tighly bound nuclides (ex: Fe) are hard to pull apart. The least tightly bound nuclides are the light elements (ex: H) and the very heavy ones (ex: Ur). Binding energy can be gained by fusion of light elements and fission of heavier ones.
What is a Fusion Reaction?
The fusion of atoms is the process of smashing isotopes (usually light elements) together to create a more stable atom and other fusion nuclide products (neutrons), therefore releasing fusion energy in the form of heat.
(Example: Deuterium (2*H) and Tritium (3*H) to make a stable He atom, and a neutron).
What is a Fission Reaction?
A fission reaction is type of reaction in which a nucleus splits into smaller parts, converting mass into kinetic energy (i.e. heat then to be changed to electricity).
