STRUCTURE OF MATTER & ELECTROMAGNETIC ENERGY Flashcards
What is an atom?
The smallest particle that has all the properties of an element.
What are the fundamental particles of an atom?
Electron, proton, and neutron.
What does “atomos” mean?
Indivisible.
What are the four substances in the Greek atom?
Earth, water, air, and fire.
What are the four essences in the Greek atom?
Wet, dry, hot, and cold.
How many elements are identified?
112 (92 naturally occurring, 20 artificially produced).
Particles smaller than an atom.
SUBATOMIC PARTICLES
Who proposed the “hook-and-eye” atomic model?
John Dalton (1808).
What did Dmitri Mendeleev create?
The first periodic table of elements.
What are alkali metals?
Group 1 elements, soft metals that react violently with water.
Group VII elements that combine with metals to form water-soluble salts.
halogens
What are noble gases?
Group VIII elements highly resistant to chemical reactions.
What is the Thomson atomic model?
Plum pudding model with electrons (negative charges) embedded in a positive mass.
Who investigated the properties of cathode rays?
J.J. Thomson in the 1890s.
Describes an atom with a dense, positively charged nucleus surrounded by electrons.
Rutherford atomic model
Who improved Rutherford’s atomic model?
Niels Bohr in 1913, proposing the miniature solar system model.
A theory describing atomic structure in detail.
quantum chromodynamics (QCD)
A device used to map the structure of atomic nuclei.
particle accelerator
Protons and neutrons in the nucleus, composed of quarks and gluons.
nucleons
What is the relative mass of an electron?
9.1 x 10^31 kg
What is the relative charge of a proton?
+1
Where are electrons located in an atom?
In the orbital shells.
What is the mass of a neutron in amu?
1.00867 amu.
Define atomic mass unit (amu).
The mass of a neutral atom, equivalent to 1/12 the mass of a carbon-12 atom.
What does the atomic mass number represent?
The sum of protons and neutrons in the nucleus.
What determines the chemical behavior of an atom?
number of protons.
Define isotopes.
Atoms with the same number of protons but different numbers of neutrons.
What is centripetal force?
The center-seeking force that keeps electrons in orbit.
What is centrifugal force?
The outward force that causes electrons to travel away from the nucleus.
The strength of attachment of an electron to the nucleus.
electron binding energy
What are the primary constituents of x-ray tube targets?
Tungsten (W-74) and molybdenum (Mo-42).
Which elements are used as contrast agents?
Barium (Ba-56) and iodine (I-53).
What is ionization potential?
The energy (34 keV) needed to ionize tissue atoms.
What is the symbol for atomic number?
Z
What is the symbol for atomic mass number?
A
A group of atoms forming the smallest unit of a compound.
molecule
What percentage of the human body is water?
80%
A chemical bond formed by the sharing of electron pairs.
covalent bond
A bond formed by the electrostatic force between ions.
ioninc bond
What is radioactivity?
The emission of particles and energy to achieve nuclear stability.
The process where unstable nuclei emit particles and energy, transforming into other atoms.
radioactive decay
Radioactive atoms with the same number of protons but varying numbers of neutrons.
radioisotopes
What occurs during beta emission?
A neutron converts to a proton, increasing the atomic number by one.
What occurs during alpha emission?
The nucleus loses 2 protons and 2 neutrons, reducing its mass by 4 amu.
What is radioactive half-life?
The time required for radioactivity to decrease to half its original value.
Half-life of iodine-131?
8 days
Half-life of carbon-14?
5730 years.
What is the primary difference between x-rays and gamma rays?
Their origin: x-rays from electron clouds, gamma rays from the nucleus.
Define particulate radiation.
Radiation with mass, such as alpha and beta particles.
What is an alpha particle?
A helium nucleus consisting of 2 protons and 2 neutrons.
What is the range of alpha particles in air?
1–10 cm.
What is a beta particle?
A high-speed electron or positron emitted from the nucleus.
What is the energy range of beta particles?
0–7 MeV.
What is the energy of an x-ray photon?
0–25 MeV.
Massless bundles of electromagnetic energy traveling at the speed of light.
photons
What is the speed of light?
3x10^8 or 186,000 miles/s.
Define electromagnetic energy.
Energy in the form of waves, such as x-rays, microwaves, and visible light.
Who demonstrated the electric and magnetic properties of light?
James Clerk Maxwell.
Half the range from crest to valley of a sine wave.
amplitude
The distance between successive crests or valleys of a wave.
wavelength
Define frequency.
The number of wave cycles passing a point per second.
What is the unit of frequency?
Hertz
What is the relationship between wavelength and frequency?
inversely proportional
What is the visible light range in the electromagnetic spectrum?
400 nm (violet) to 700 nm (red).
What is refraction?
The bending of light as it passes from one medium to another.
Infrared radiation that heats substances.
radiant heat
Electromagnetic waves with long wavelengths and low energy, used in MRI.
radiofrequency
What is the energy range of gamma rays?
0–5 MeV.
What is the inverse square law?
Intensity is inversely proportional to the square of the distance from the source.
What is Planck’s constant?
6.63 X 10^-34 Js
Planck’s quantum equation?
E=hf, where E is energy, h is Planck’s constant, and f is frequency.
What is the relationship between photon energy and frequency?
Directly proportional.
The principle that electromagnetic energy exhibits both wave-like and particle-like properties.
wave-particle duality
How does visible light behave?
like a wave
How do x-rays behave?
like particles
What is electromagnetic energy attenuation?
Reduction in intensity due to scattering and absorption.
What is radiopaque material?
Material that absorbs x-rays, e.g., bones.
What is radiolucent material?
Material that transmits x-rays, e.g., lung tissue.
What are Grenz rays?
X-rays with energy between 10–20 kVp, used in medicine.
What is orthovoltage radiation?
X-rays with energy between 200–300 kVp.
Law of Conservation of Matter
Matter cannot be created or destroyed.
What are the three regions of the electromagnetic spectrum important to radiology?
Visible light, x-ray, and radiofrequency regions.
What is the significance of the x-ray region in radiology?
Fundamental to producing high-quality radiographs.
What is the purpose of visible light in radiology?
Critical for viewing radiographic and fluoroscopic images.
What is the range of radiofrequency used in MRI?
1–100 MHz.
What is the unit of photon energy?
Electron volt (eV).
What is the energy of x-rays produced in diagnostic imaging?
30–150 keV.
What are diffraction x-rays used for?
Research.
Define transparency in electromagnetic interactions.
No attenuation, e.g., clear window glass.
Define translucency in electromagnetic interactions.
Partial attenuation, e.g., frosted glass.
Define opacity in electromagnetic interactions.
Complete absorption, e.g., black glass.
The graphical representation of electromagnetic wave variation.
sine wave
What is the principal quantum number?
The shell number of an electron in an atom.
What does a neutral atom contain?
Equal numbers of protons and electrons.
What is the most significant isotope in human tissue?
carbon-12
What is the primary source of natural radioisotopes?
Uranium (U-92).
What is the primary artificially produced radioisotope in radiology?
Technetium-99m (Tc-99m).
What is the decay product of technetium-99m?
Technetium-99.
A continuum of electromagnetic energy arranged by frequency and wavelength.
electromagnetic spectrum.
What is the frequency range of the electromagnetic spectrum?
10^2 to 10^24 Hz
What is the wavelength range of the electromagnetic spectrum?
10^7 to 10^-16 m
Define diffraction x-rays.
X-rays with energy <10 keV used in research.
What are superficial x-rays used for?
Medical applications, energy range 50–100 kVp.
Define megavoltage radiation.
Radiation with energy >1 MV, used in medicine and industry.
A positive beta particle (antimatter of an electron).
positron
What is the ionization rate of alpha particles?
40,000 ion pairs/cm.
What is the ionization rate of beta particles?
Several hundred ion pairs/cm.
What is the ionization rate of x-rays?
100 ion pairs/cm.
The smallest quantity of electromagnetic energy.
photon
What is the range of x-rays in soft tissue?
0–30 cm.
What is the mass of x-rays and gamma rays?
0
What is a neutron’s charge?
Zero (neutral).
A chart organizing elements by increasing atomic number.
periodic table
What are the 4 abundant elements found in the human body
CHON
Carbon
hydrogen
oxygen
nitrogen
