Ch. 2 The Structure of Matter Flashcards
Break down the word atom
a (not) + temon (cut) (indivisible)
How many elements have been identified?
118
How many elements are natural and how many artificially produced?
92 natural and 26 artificial
An atom is…
the smallest particle of matter that has the properties of an element
Whose work brought about the first periodic table of elements?
Dmitri Mendeleev
Where is the atomic # and where is the elemental mass?
Atomic # is above the element symbol and the atomic mass is below.
groups are in….
columns
How are elements in groups similar?
They react chemically in a similar fashion and have similar physical properties
Elements in group I are all soft metals (alkali metals) and combine readily with oxygen and react violently with water except…
Hydrogen
What are the elements in group VII called?
halogens
What are the elements in group VIII called?
noble gases
How are elemental groupings determined?
By the placement of electrons in each atom
Cathode rays are also called…
electrons
What type of charge are electrons?
negatively
What is the newer model of the atom called?
quantum chromodynamics (QCD)
Describe the Bohr Atom
A small, dense, positively charged nucleus surrounded by negatively charged electrons that revolve in fixed, well-defined orbits about the nucleus.
In a normal atom, what is equal to what?
the number of electrons is equal to the number of positive charges in the nucleus
What is an atom smasher?
a particle accelerator
What are nucleons?
protons and neutrons that are composed of quarks that are held together by gluons
What are the primary constituents of an atom in radiologic science?
electron, proton and neutron
What are the fundamental particles of radiology?
electron, proton, and neutron
What determines how an atom will interact?
The arrangement of electrons around the nucleus.
Electrons are very small particles that carry…
one unit of negative electric charge
What is the mass of an electron?
9.1 x 10^-31
How is the mass of an atom expressed?
in atomic mass units (amu)
When precision is not necessary, what is used instead of the amu?
the atomic mass number, which is always a whole number
Where are nucleons?
In the nucleus
How many different types of nucleons are there and what are their names?
2 types; protons and neutrons
Describe the mass of protons and neutrons.
They have nearly 2000 times the mass of an electron
Which is heavier, a proton or neutron?
Neutron by 0.002 kg
What is the primary difference between a proton and neutron?
electric charge
What is the electric charge of a proton and of a neutron?
a proton has one unit of positive electric charge and a neutron carries no charge
An atom is mostly…
empty space
What contains nearly all the mass of an atom?
the nucleus
Electron orbits are called..
shells
What do the shells do?
The arrangements of the shells helps reveal how an atom reacts chemically, or how it combines chemically with other atoms to form molecules
A neutral atom has the same….
number of electrons in orbit as protons in the nucleus
What part of the nucleus in a neutral atom determines the chemical behavior of an atom?
the number of protons
What determines the chemical element of an atom?
the number of protons
What are isotopes?
Atoms that have the same number of protons but differ in the number or neutrons
How many protons and electrons are in an atom of hydrogen?
1 and 1
What do the shells represent?
different electron binding energies or energy levels
When is the binding energy of an electron the greatest?
the closer it is to the nucleus
In what state are atoms electrically neutral?
in their natural state their charge on the atom is zero
The total number of electrons in the orbital shells equals what?
the number of protons in the nucleus
When is an atom ionized?
If an atom has an extra electron or has had an electron removed
The number of neutron is always
greater than the number of protons
The maximum number of electrons that can exist in each shell _______ with the distance of the shell from the nucleus.
increases
What is the formula that calculates the electron limit per shell?
2n^2
What is the principal quantum number?
the shell number n
The number of electrons in the outermost shell is:
- Equal to its group in the periodic table
2. Determines the valence of an atom
The number of the outermost electron shelll is:
equal to its period in the periodic table
No outer shell can contain more than..
8 electrons
Atoms with 8 outer shells and lie in group VIII are considered ____ and are called _____ _____ and are ____.
filled; noble gasses; stable
What are transitional elements?
When the orderly scheme of atomic progression from smallest to largest atom is interrupted in the 4th period and instead of adding electrons to the next outer shell, electrons are added to an inner shell.
The chemical properties of the transitional elements depend on what?
the number of electrons in the 2 outermost shells.
Why doesn’t an electron fly off from the nucleus?
Because of centripetal force.
What is the basic law of electricity?
That opposite charges attract one another and like charges repel.
What does centrifugal force do?
allows electrons to maintain their distance from the nucleus while traveling in a circular or elliptical path.
Define electron binding energy.
The strength of attachment of an electron to the nucleus
How do we know if an electron is more tightly bound than another?
The closer an electron is to the nucleus, the tighter it is bound.
The greater the total number of ____ in an atom, the more ___ they are bound.
electrons; tightly
What 2 metals are commonly used as the targets in an x-ray tube?
Tungsten and molybdenum
What 2 chemicals are used as radiographic and fluoroscopic contrast agents?
barium and iodine
How much energy is required to ionize tungsten through removal of a K-shell electron?
The minimum energy must equal 69 keV
What value is ionization potential?
34 eV
Chemical properties of an element are determines by…
the number and arrangement of electrons
In a neutral atom, what equals what?
the number of electrons equals the number of protons
What is the number of protons called?
the atomic number, represented by Z
What is the atomic mass number?
The number of protons plus the number of neutrons int he nucleus, represented by A
The atomic number is always a …
whole number
Define an isotone
atoms with different atomic numbers and different mass numbers but a constant value for the quantity A-Z. Also, isotones are atoms with the same number of neutrons int he nucleus
What is an isomer?
they have the same atomic number and the same atomic mass number
Isomers are identical atoms except for what?
that they exist at different energy states because of differences in nucleon arrangement.
Define molecule
Atoms of various elements may combine to form structures called molecules
What is formed when 2 hydrogen and 2 oxygen atoms are combined?
a molecule of water
What is a chemical compound?
any quantity of one type of molecule
What composes more than 95% of the human body?
hydrogen, oxygen, carbon, and nitrogen
What is the % of the human body is water?
80%
What do the subscript and superscript to the left of the chemical symbol represent?
atomic number and atomic mass number
What do the subscript and superscript to the right of the chemical symbol represent?
values for the number of atoms per molecule and the valence state of the atom, respectively
oxygen and hydrogen combine into water through what kind of bond?
covalent bond
Covalent bond is characterized by what?
the sharing of electrons
Sodium and chlorine combine into salt through what kind of bond?
ionic bond
An atom has become ionized when…
it has lost or gained an electron and has an imbalance of electric charges
2 ionized atoms are attracted to each other because…
they have opposite electrostatic charges
What is the smallest particle of an element?
an atom
What is the smallest particle of a compound?
a molecule
What is radioactive disintegration or radioactive decay?
When a nucleus spontaneously emits particles and energy and transforms itself into another atom because it has been existing in an abnormally excited state characterized by an unstable nucleus
What atoms are involved in radioactive decay?
radionuclides
Define nuclide
any nuclear arrangement
Only ____ that undergo radioactive decay are _______
nuclei; radionuclides
What is radioactivity?
the emission of particles and energy in order to become stable
What happens if an atom has too many or too few neutrons?
The atom can disintegrate radioactively, bringing the number of neutrons and protons into a stable and proper ratio.
What is a radioisotope?
radioactive isotopes
What does uranium decay into?
radium and then into radon
What happens during beta emissions?
an electron created in the nucleus is ejected from the nucleus with considerable kinetic energy and escapes from the atom. This results in a loss of a small quantity of mass and 1 unit of negative electric charge from the nucleus of the atom. Simultaneously, a neutron undergoes conversion to a proton.
What is the result of a beta emission?
it increases the atomic number by 1, while the atomic mass stays the same. Changing the atom from one type to another.
What happens during an alpha emission?
The alpha particle consists of 2 protons and 2 neutrons bound together. When the nucleus emits an alpha particle, it loses 2 units of positive charge and 4 units of mass. This is a big change cause the atom is chemically different and also lighter by 4 amu.
What does radioactive decay result in?
emission of alpha particles, beta particles, and usually gamma rays.
What happens more? Beta or alpha emissions?
Beta…much more!
What is half life of a radioisotope?
the time required for a quantity of radioactivity to be reduced to one half its original value
What is the radioactive decay law?
the rate of radioactive decay and the quantity of material present at any given time that are described mathematically by a formula.
What is the formula for half life?
T1/2
All ionizing radiation can be classified into 2 categories:
- particulate radiation
2. electromagnetic radiation
What are the types of radiation used in diagnostic ultrasonography and MRI?
nonionizing radiation
What are capable of causing ionization?
Many subatomic particles
There are 2 main types of particulate radiation:
Alpha and beta particles
What is a helium nucleus that contains 2 protons and 2 neutrons?
an Alpha particle
What type of range does an alpha particle have in matter?
A very short range due to its low amount of ionization. Because of this, its energy of an alpha particle is quickly lost.
In air, how far can an alpha particle go? Soft tissue?
about 5cm; it may be less than 100 microunits
Alpha radiation from an external source is nearly _____. Why?
Because the radiation energy is deposited in the superficial layers of the skin
Describe a beta particle
They are light particles with an atomic mass number of 0 and carry 1 unit of either negative or positive charge.
What is the difference between electrons and negative beta particles?
Their origin. Beta particles originate in the nuclei of radioactive atoms and electrons exist in shells outside the nuclei of all atoms.
What are positive beta particles called?
positrons
After leaving a radioisotope, beta particles go through air, ionizing…
several hundred atoms per centimeter
How far can a beta particle go?
10 - 100 cm of air and about 1 - 2 cm of soft tissue
Name 2 types of electromagnetic ionizing radiation
x-rays and gamma rays
What is another name for x-ray and gamma rays?
photons
photons have no ___ and no ____
mass, charge
How fast do photons travel?
nearly the speed of light and considered energy disturbances in space
What is the difference between x-rays and gamma rays?
Their origin
Where are gamma rays emitted?
from the nucleus of a radioisotope and associated with alpha or beta emission
Where are x-rays made?
outside the nucleus in the electron shell
x-rays and gamma rays go the speed of light or…
not at all
x-rays and gamma rays equal about the same speed in air as…
beta particles
How do x-rays and gamma rays differ?
x-rays and gamma rays have an unlimited range in matter
Photon radiation loses intensity with distance but….
theoretically never reaches 0
Particulate radiation has a ______ range in matter and depends on what?
finite; the particle’s energy
What type of radiation is most important in nuke med; and what type for radiography?
beta and gamma for nuke med
x-rays for radiography
Why are x-rays so useful for medical imaging?
because of their penetrability and low ionization rate
