Radiation Concepts - Atomic Structure

QUIZ on 9/5/23; TEST on 9/7/23

What does Å stand for?

Ångstrom

Define Angstrom

The subatomic unit of distance equal to 10^-10 meters, used to measure wavelength

Define matter

Has form or shape and occupies space (all physical objects are made of matter)

Define substance

A material with a definite and constant composition

Define element

A simple substance which cannot be broken down into any simpler substance by ordinary means

Define compound

A complex substance made of two or more elements that are chemically united in definite proportions

Define atom

Smallest particle of an element that still possesses chemical properties of that element

In radiology, interactions occur at the atomic level within ___, ___, and ___

the X-ray tube, the human body, and the image receptor (IR)

How do you find the atomic number?

Determined by the number of protons in an atom (unique to each element)

What is another term for atomic number?

Z number

Define proton

Positively charged particle found in the nucleus of an atom (determines the atomic number)

Define neutron

Subatomic particle found in the nucleus of an atom; has no charge (is considered neutral)

Define nucleon

A nuclear particle (includes protons and neutrons)

What does A stand for?

Atomic mass

Define atomic mass

Amount of matter in an object (generally considered the same as weight)

Define weight

force that object exerts under influence of gravity

How do you find atomic mass?

The total number of nucleons in an atom (protons + neutrons)

Define electron

A negatively charged subatomic particle that orbits the nucleus and has essentially no weight

Define covalent bond

Occurs when two atoms share their unpaired electrons (the most common form of bonding)

Do covalent bonds form a strong or weak bond?

Weak

Define ionic bond

Atoms with opposite charges are attracted and pulled together; atoms exchange electrons to become stable

Do ionic bonds form a strong or weak bond?

Strong

Define ionization

The process of adding or removing an electron from an atom

What is the periodic table?

A table of elements listed in order of their atomic (or Z) number; elements in the same column have similar chemical properties

Define radiation

Energy that is emitted and transferred through space/matter

Define isotope

Atoms of an element that have the same number of protons but a different number of neutrons (makes the atom unstable which results in radioactivity)

Define radionuclide

Any atom that is radioactive (unstable)

Define radioisotope

any atom which is radioactive because it has too few or too many neutrons

Define radioactive decay

the loss of any mass or energy from the nucleus of an atom (radioactive element gives off excess energy to regain stability)

Define half-life

the length of time it takes for decay to half intensity

Define electron binding energy

the amount of energy needed to remove the electron from the atom

Define frequency

the number of waves passing a particular point in a given time

Define photon

a small bundle of energy (amount of energy depends on the frequency)

Define valence

the number and configuration of the electrons in the outer shell

Define the octet rule

the number of electrons in the outer shell of an atom never exceeds 8 electrons

What happens when there are exactly 8 electrons in the outer shell?

atom is considered inert and chemically stable

What is the K shell?

the orbital shell closest to the nucleus

What does dual nature (Wave Particle Duality) of X-rays mean?

X-rays travel in waves but behave as a particle when interacting with matter

What is an X-ray photon?

a bundle of energy present when an X-ray is behaving as a particle

What is the speed of light?

186,400 miles per second in a vacuum

3 x 10^8 meters per second in a vacuum

What is the wavelength of X-rays?

0.1 - 0.5 Å

Define energy

the ability to do work

What are the two types of mechanical energy?

potential and kinetic

Define kinetic energy

energy of motion (wind and/or water)

Define potential energy

energy of position

Define chemical energy

energy resulting form a chemical reaction

Define electrical energy

energy that is emitted and transferred through matter; movements of electrons

Define thermal energy

energy resulting from movement of atoms or molecules

Define nuclear energy

energy resulting from the nucleus of an atom

Define electromagnetic energy

energy that is emitted and transferred through matter

What is a complex substance called?

compound

What is a simple substance called?

element

What is the simplest form of a compound?

molecule

What is the simplest form of an element?

atom

Define mixture

2+ substances stirred together but not chemically bound

Define molecule

the smallest unit of a chemical compound

What does the Bohr model depict?

a mini solar system with electrons orbiting the nucleus in many planes

What does the Quantum Mechanics model depict?

atom is mostly space; 7 electron energy levels, orbital shells, orbits not concentric

Neutrons and protons are approximately ___ times the size of an electron

2,000

A stable/neutral atom has the same number of ___ and ___

protons and electrons

There are ___ naturally occurring elements and ___ lab-created elements

92 naturally occurring

18 lab-created

What are the elements that are important to radiography?

Hydrogen, Helium, Carbon, Oxygen, Aluminum, Calcium, Iodine, Barium, Tungsten, Rhenium, and Lead

What does amu stand for?

atomic mass units

If an atom gains or loses a neutron, it becomes a(n) ___

isotope

Define electron binding energy

the amount of energy needed to remove the electron from the atom

What is electron binding energy measured in?

electron volts = eV

Electron orbital shells are labeled starting with ___ and ending with ___

starting with K and ending with Q

The closer to the nucleus, the binding energy is ___ (greater or weaker)

greater

Binding energy ___ (gets weaker or gets stronger) as you get farther from the nucleus

gets weaker

Binding energy increases as the number of ___ and ___ increase in an atom

electrons and protons (high atomic number elements are bound more tightly than low atomic number elements)

What is the equation for determining the maximum number of electrons that can occupy each electron shell?

2 n^2

where n is the shell number

In the 3rd electron shell (M), what is the maximum number of electrons that can occupy the shell?

2 n^2

2 (3^2)

2 (9)

18 electrons

Define ion

any electrically charged particle

Atom with an extra e- is ___

negative

Atom that loses an e- is ___

positive

What is the result of ionization?

free e- that is available to move on to interact with another atom

Describe the Law of Conservation of Energy

matter and energy cannot be created nor destroyed, but can be converted

e=mc^2

What is a Joule?

unit of energy

From low frequency to high frequency, list the electromagnetic spectrum

Radio → Microwave → Infrared → Visible(ROYGBIV) → Ultraviolet → X-ray → Gamma Ray

Electromagnetic energy is equal to the ___

speed of light

What is the wave theory?

electromagnetic waves travel in a sine wave

• wavelength (λ)

  • distance of one full wave (X-ray is 0.1-0.5 Å)

• amplitude

  • height of a wave (above the x-axis)

• frequency

  • the number of waves passing a specific point in a given time

• period

Any electrically charged particle that is moving generates a ___ magnetic field

perpendicular

A magnetic field forms at a 90-degree angle to a(n) ___

electrical current

Average radio waves are about ___, whereas microwaves are about ___

radio waves: 1 mile long

microwaves: 1 cm long

Are X-rays bigger or smaller than an atom?

smaller

If frequency goes up, wavelength goes ___

down

(they are inversely/indirectly proportional)

What is the wave equation?

v = f λ

velocity = frequency x wavelength

What is Plank’s Formula?

E = hf

(photon energy) = (Planck’s constant) x (photon frequency)

Photon frequency is measured in ___

Hz

When photon energy goes up, frequency goes ___

up

(they are directly proportional)

Describe Alpha particles

• 2 protons bound to 2 neutrons

• do not travel far

• cannot penetrate most objects

Define Beta particles

• electron emitted from unstable nucleus

• large range

  • may ionize many atoms along its path

What date did Wilhelm Conrad Roentgen come up with the 12 properties of X-rays?

November 8, 1895

How many of Roentgen’s properties have been proven false?

none

What are the 12 properties of X-rays? (must know at least 4)

• highly penetrating, invisible rays which are a form of electromagnetic radiation

• are electrically neutral and not affected by electric or magnetic fields

• can be produced over a wide variety of energies and wavelengths (polyenergetic/heterogenous)

• release a small amount of heat when passing through matter

• travel in straight lines

• travel at the speed of light

• can ionize matter

• cause fluorescence (emission of light) of certain crystals

• cannot be focused by a lens

• affects photographic film

• produces chemical and biological changes in matter through ionization and excitation

• produces secondary and scatter radiation