Characteristics and Structure of Matter Flashcards
Where is radiation created and then later absorbed within?
Some material substance or matter
Where does radiation interaction occur (both formation and absorption)?
within individual atoms
What are the two major regions of atoms?
- Nucleus
2. Electron shells
What is the nucleus a source of?
Source of energy for the radiation used in nuclear medicine procedures
What is the nucleus involved in?
Production of x-ray photons
How is radiation absorbed?
Interacting with electrons located in the shells surrounding the nucleus
How is one form of x-radiation produced?
Transition in the shell electrons
What is the conventional model of atoms consisting of nucleus?
protons and neutrons surrounded by electrons located in specific orbitals or shells
How is the nucleus shown?
A ball or cluster of particles at the centre of atom
What is quite small in comparison to the total dimension of atom?
Nucleus
What is contained within the nucleus?
Most of mass of atom
What is located at a much greater distance from the nucleus?
Electrons
What are two basic particles of nuclei?
- Neutrons
2. Protons
What is almost the same size but differ in their electrical charge?
- Neutrons
2. Protons
What has no electrical charge and contribute only mass to the nucleus?
Neutrons
What does proton have a positive charge equal in strength to?
Negative charge carried by an electron
What relates to nuclei’s neutron-proton composition?
Physical and chemical characteristics of a substance
What establishes the chemical identity of the atom?
The number of protons in a nucleus (atomic number [Z])
What does each atomic number correspond to?
Different chemical element
Why is not convenient to express the mass of nuclei and atomic particles in the conventional unit of kilograms?
Very small size
What is the relationship between atomic mass unit and kilogram?
1 amu = 1.66 x 10-27 kg.
What is difference in mass between a neutron and proton?
Quite small
approx 0.1%
What is required to equal the mass of a proton or neutron?
More than 1,800 electrons
What is the mass number (A)?
The total number of particles (neutrons and protons)
What is proportional to the mass number?
The total mass or weight of a nucleus
What happens when nucleus is formed?
Some of the mass is converted into energy
What does lighter element contain?
Almost equal numbers of neutrons and protons
What is the consequence of the size of the nucleus increasing?
The ratio of neutrons to protons increases to a maximum of about 1.3 neutrons per proton for material with very high atomic numbers
How is the number of neutrons in a specific nucleus obtained?
Subtracting the atomic number from the mass number
What can one chemical element have?
Nuclei containing different numbers of neutrons
What determines if a nucleus is radioactive?
The variation in neutron composition
How many different atomic numbers or elements are there?
106
How many different neutron-proton combinations are now known?
at, least 1,300
Define Isobars?
Nuclides having the same mass number but different atomic numbers
What cannot belong to the same chemical element?
A pair of isobars
Define isomers
Two nuclei that have the same composition but varying energy
What will a nucleus in the metastable state give off?
Its excess energy and change to the other isomer
Define Isotones
Nuclides that have the same number of neutrons
What is the ability of a nucleus to emit radiation energy related to?
Level of stability
What is nuclear stability determined by?
Balance of forces within the nucleus
What is a significant factor that determines the balance between internal forces and therefore nuclear stability?
The ratio of number of neutrons to the number of protons
When will the nucleus be generally radioactive?
If the neutron-proton ratio is slightly above or below the ratio for stability
When does a nucleus emit energy?
When it changes to a more stable form
What process creates energy?
The fusion of two small nuclei to form a larger nucleus
How is radiation energy created?
When nuclei undergo spontaneous radioactive transitions to create more stable nuclear structures
What will the mass of 1g completely converted produce?
25,000,000 kilowatt-hours
What are clinical applications interested in?
Amount of energy released by an individual atom
What is kiloelectron volts (keV)?
A relatively small unit of energy
What is the relationship between some other energy units and keV?
1 erg = 6.24 x 108 keV
1 j = 107 erg = 6.24 x 1015 keV.
What is the energy equivalent of one electron mass?
511 keV
referred to as the rest-mass energy of an electron
What does orbital electrons become involved in?
Actual emission of energy from the atom
Where are electrons located in?
orbits or shells in the space surrounding a nucleus
What is the atomic number?
The number of electrons contained in a normal atom equal to the number of protons in the nucleus
What does a shell have?
Limited electron capacity
What is the maximum capacity of the K, L, M shells?
K - 2
L- 8
M-18
How are electrons bound to the positive nucleus of an atom?
Negative electrical charge
What is binding energy a form of?
Electron potential energy
What is designated the zero point?
A location outside the atom where the electron is no longer under the influence of nucleus
Which shell is closest to the nucleus?
K shell
Lowest energy level
Define ionization
The removal of an electron from an atom
What is considered ionizing radiation?
X-ray and gamma photons
sufficient energy to remove electrons from atoms
What cannot produce ionization?
Visible light
When are photons absorbed?
When they collide with electrons
