Radiation And The Atom Flashcards
The interaction of electromagnetic radiation can occur by what ways?
By scattering (change in trajectory), absorption (removal of radiation), or at very higher energies, transformation into particulate radiation (energy to mass conversion)
What are the two ways of describing EM radiation?
As waves and as discrete particle-like packets or quanta of energy called photons.
What characteristic is more apparent when EM radiation interacts with objects of similar dimensions as the photon’s wave length?
Wave characteristics
These characteristics of EM radiation are more evident when an object’s dimensions are much smaller than the photon’s wavelength.
Particle characteristics
The particle-like behaviour of x-rays is exemplified by the classical “billiard-ball” type of collision between an x-ray photon and an orbital electron during _______ event.
Compton scattering
Wave characteristics
Any wave (EM or mechanical,such as sound) can be characterised by their ______, ______, _____, and ______.
Amplitude (maximal height)
Wavelength
Frequency
Period
This is the intensity of the wave
Amplitude
This is the distance between two identical points on adjacent cycles.
Wavelength
The time required to complete one cycle of wave is the _____.
Period
The number of periods that occur per second is the _______.
Frequency
Because speed of EM radiation is constant in a given medium, it’s frequency and wavelength are ______ proportional.
Inversely
Discrete (particle-like) packets (or quanta) of EM energy are called ______.
Photons
Wavelength of x-rays and gamma rays are typically measured in fractions of _______.
Nanometer
1 nm = 10 to the negative 9 nm
Frequency is expressed in _____.
Hertz (Hz)
Energies of photons are commonly expressed in ______.
Electron volts (eV)
It is defined as the energy acquired by an electron as it traverses an electrical potential difference (voltage) of one volt in a vacuum.
One electron volt
Multiples of the eV common to medical imaging are the keV (1,000 eV) and the MeV (1,000,000 eV)
An atom or molecule that has lost or gained one or more electrons has a net electrical charge and is called ______.
Ion
In general, photons of higher frequency than the far UV region of the spectrum (wavelengths greater than 200 nm) have sufficient energy per photon to remove bound electrons from atomic shells, thereby producing ionized atoms or molecules.
Radiation in this portion of the spectrum is called?
Ionizing radiation
EM radiation with photon energies in and below the UV region is called?
Nonionizing radiation
What is ionization energy?
The minimum energies necessary to remove an electron
This property of particulate radiation has a positive electrical charge and is identical to the nucleus of a hydrogen atom.
Protons
Protons are found in the nuclei of all atoms
Electrons emitted by the nuclei of radioactive atoms are referred to as _______.
Beta particles
Except for their nuclear origin, negatively charged beta minus particles, or negatrons, are indistinguishable from ordinary orbital electrons
These are positively charge electrons.
They are are form of antimatter that ultimately combines with matter in a unique transformation in which all of their mass is instantaneously converted to an equivalent amount of energy in the form of high-energy gamma rays.
Beta plus particles or positrons
A ________ is an uncharted nuclear particle that has a mass slightly greater than that of a proton.
They are released by nuclear fission and are used for radionuclide production.
Neutron
These particle consists of two protons and two neutrons; it thus has +2 charge and is identical to the nucleus of a helium atom.
They are emitted by many high atomic number radioactive elements, such as uranium, thorium, and radium.
Alpha particles
These particles emitted outside the bodyare harmless, alpha particles emitted inside the body cause more extensive cellular damage per unit energy deposited in tissue than any type of radiation used in medical imaging
The _____ is the smallest division of an element in which the chemical identity of the element is maintained.
It is composed of an extremely dense positively charged nucleus, containing protons and neutrons, and an extra nuclear cloud of light negatively charged electrons.
Atom
In its _______ state, an atom is electrically neutral number of protons equals the number of electrons.
Nonionized state
The innermost shell of an atom, in which the electrons have the lowest energies.
K shell
The outer electron shell of an atom, the _____ shell, determines the chemical properties of the element.
Valence shell
It is the energy required to remove an orbital electron completely from the atom.
Orbital binding energy
For radiation to be ionizing, the energy transferred to the electron must be ____________ its binding energy.
Equal or exceed
Due to the closer proximity of the electrons to the positively charged nucleus, the binding energy of the K-shell is _______ than that of the outer shells.
Greater than
When an electron is removed from its shell by an x-ray or gamma ray photon or a charged particle interaction, a vacancy is created in that shell.
This vacancy is usually filled by an electron from an outer shell, leaving a vacancy in the outer shell that in turn may be filled by an electron transition from a more distant shell.
This series of transitions is called _____?
Electron cascade
Emissions from transitions exceeding 100 eV are called ______.
Characteristic or fluorescent x-rays
Characteristic x-rays are named according to the orbital in which vacancy occurred. Ex. K-characteristic x-ray)
An electron cascade does not always result in the production of a characteristic x-ray or x-rays.
A competing process that predominates in low Z elements is _______________.
Auger electron emission
In this case, the energy released is transferred to an orbital electron, typically the same shell as the cascading electron
The ejected Auger electron possesses kinetic energy equal to the difference between the transition energy and the binding energy of the ejected electron.
The probability of the electron transition will result in the emission of a characteristic x-ray is called the __________.
Fluorescent yield
The nucleus is composed of protons and neutrons, known collectively as _______.
Nucleons
The number of protons in the nucleus is the _________ number, and the number of protons and neutrons within the nucleus is the ______ number.
Atomic number
Mass number
The _______ force between the protons is repulsive and countered by the attractive force resulting from the exchange of gluons (subnuclear particles) among the nucleons.
Coulumbic force
The exchange forces, also called the strong force, hold the nucleus together but operate only very short (nuclear distances)
The lowest energy state of a atomic nucleus is called the ______.
Ground state
Nuclei with energy excess of the ground state are said to be in an _______ state.
Excited state.
Excited states that exist longer than 10 (-12) s are referred to as ________.
Meta stable or isomeric states
Species of atoms characterized by the number of protons and neutrons and the energy content of the atomic nuclei are called _______.
Nuclides
Nuclides that decay (i.e., transform) to more stable nuclei are said to be _________, and the transformation process itself is called _________.
Radioactive
Radioactive decay (radioactive disintegration)
The EM radiation emitted from the nucleus as the excited state transitions to lower (more stable) energy state is called ________.
Gamma ray
This energy transition is analogous to the emission of characteristic x-rays following electron transition
When the nuclear de-excitation process takes place in an isomer (e.g., Tc-99m), it is called ______.
Isomeric transition
W
In isomeric transition, the nuclear energy state is reduced with no change in A or Z
Nuclear de-excitation process does not always result in the emission of a gamma ray.
An alternative form of de-excitation is _______, in which the de-excitation energy is completely transferred to an orbital electron.
Internal conversion
The energy required to separate an atom into its constituent parts is the _________.
It is the sum of the orbital electron binding energy and the nuclear binding energy.
Atomic binding energy
It is the energy necessary to disassociate a nucleus into its constituent parts and is a result of the strong forces acting between the nucleons.
Nuclear binding energy
The binding energy can be calculated by subtracting the mass of the atom from the total mass of its constituent protons, neutrons, and electrons; this mass difference is known as the _________.
Mass defect
During nuclear fission, a nucleus with large atomic mass splits into two usually unequal parts called _________, each with an average binding energy per nucleon greater than that of the original nucleus.
Fission fragments
