intro to module Flashcards
what is an atom.
can it be divided and how many parts?
Smallest unit of matter that has the characteristic properties of a chemical element
Smallest unit into which matter can be divided without the release of electrically charged particles;
Electrons
Protons
Neutrons
what is an element
how many atoms is the element made up of
how many elements
Distinct kind of matter which cannot be broken down into two or more smaller kinds of matter
Always made up of the same atom
118 elements have been identified (organised in the Periodic Table)
what is the atomic structure
Electrons : negatively charged particles orbiting the nucleus of an atom. The charge on a single electron is -1.6 x 10 -19 Coulomb.
Protons: positively charged particle. The charge on a single proton is +1.6 x 10 -19 Coulomb.
Neutron : neutral particle with no charge.
Number electrons = number of protons so atom has no charge overall
Mass of atom is entirely in the nucleus
what is the electron configuration
Negatively charged particles orbiting the nucleus of an atom\
nucleus - proton n neutron
1st shell - 2 electrons
2nd shell - 8 electrons
electron configuration
gaining energy and losing energy
Electrons can gain energy and move one shell up (away from the nucleus)
Electrons can emit energy and move one shell down (closer to the nucleus)
what is a nuclear force
What’s holding the nucleons
What’s holding the nucleons (collective term for protons and neutrons) in the nucleus?
Laws of electromagnetic force state that like charges repel and opposite charges attract
Protons are positively charged, so why don’t they repel each other?
subatomic particles - composite particles
Composite Particles:
Can be broken down further as are made of two or more elementary particles (e.g. protons and neutrons)
subatomic particles - Elementary Particles:
Elementary Particles:
Smallest particles not made of any other particles (e.g. quarks)
Protons and Neutrons quarks how many up and down quarks do they have
Protons: 2 Up quarks and 1 Down quark
Neutrons: 1 Up quark and 2 Down quarks
Up quarks have a 2/3 positive charge
Down quarks have a 1/3 negative charge
Protons:
U+ U + D
(2/3) + (2/3) + (-1/3) = 3/3 = +1 positive charge
Neutrons:
D+ D + U
(-1/3) + (-1/3) + (2/3) = 0/3 = 0 charge (neutral)
The quarks within each proton and neutron are held together by elementary particles called Gluons which providing the binding force
nuclear force - mesons
Mesons:
Part of the Hadron particle family (particles composed of two or more quarks)
Composed of a quark and an antiquark
When the nucleons (protons and neutrons) are close together in the nucleus, meson particles are exchanged between them
This creates a strong nuclear force which pulls the nucleons together
Mesons are used to explain the properties and interactions of quarks
Atomic Stability large atoms nucleus vs small atoms nucleus
The strong binding force by mesons is mostly effective up to a nucleus size of 10−15m
Atoms with a large nucleus (large number protons and neutrons) are less stable
As the mass increases, the strong nuclear force cannot hold all the nucleons in the nucleus
atomic vs mass number
atomic - the number of protons in the nucleus of an atom
mass number - total number of protons and neutrons present in the nucleus of an atom is called the mass number.
Element Stability
Elements having an atomic number greater than 83 than to be unstable
Example: Uranium
Due to the large number of protons and neutrons, there is disintegration of the atomic structure and material becomes radioactive
nuclear force weak vs strong
Strong Nuclear Force
Holds the nucleus together
Weak Nuclear Force
Responsible for radioactive decay
Stability of an atom depends on the nuclear binding energy and strong nuclear force
Nuclear binding energy is the energy required to break the nucleus into its constituent particles
isotopes
Every element in the periodic table has multiple variations
These variations have the same atomic number (protons) but different mass numbers
The atomic number (protons) provides the chemical identity of the element
Some isotopes are stable, some are unstable
Radioisotopes
Not all isotopes are radioactive
Some isotopes are stable, some are radioactive
Unstable, radioactive isotopes are called radioisotopes/radioactive isotope
Unstable isotopes emit particles and energy and transform into a different element (different chemical properties/identity)
This transformational change is called radioactive decay
what is Electromagnetic Force
what is an Electric fields:
what is Magnetic fields:
Physical interaction that occurs between electrically charged particles
Originates from electric and magnetic fields
Electric fields:
Produced by an electric charge (electrons)
Exerts force on all other charges in the field, either attracting or repelling them (e.g. the attractive force holding the atomic nucleus and electrons together in atoms)
Magnetic fields:
The space near a magnet or an electric current where a physical field is created from a moving electric charge that creates force on other moving electric charges
what is an Electromagnetic Waves
An accelerating charged particle produces an electromagnetic (EM) wave
EM waves are electric and magnetic fields traveling through empty space at the speed of light
They transport energy through space
This energy can be delivered to charged particles a large distance away from the source
Accelerating charges produce changing electric and magnetic fields
Changing electric fields produce magnetic fields and changing magnetic fields produce electric fields
This interplay between induced electric and magnetic fields leads to propagating electromagnetic waves through free space
what is Electromagnetic Radiation
Waves radiating from electrically charged particles
Charged particles are referred to as photons are propagating (radiating) through space, carrying electromagnetic radiant energy
what is Electromagnetic Radiation what characteristics does it have
Characteristics:
Strength varies in an alternating or cyclic fashion
Distance between two consecutive +ve peaks = wavelength (λ)
Number of cycles that pass a fixed point per second = frequency (ν)
Velocity = distance travelled forward per second => λ x ν
All EM waves travel at the same velocity in a given medium (speed of light in a vacuum)
Electromagnetic Spectrum
long vs short wavelengths
The range of frequencies (spectrum) of electromagnetic radiation and their respective wavelengths and photon energies
Long wavelength = low frequency
Short wavelength = high frequency
Electrical Circuit
A path for transmitting an electric current
The circuit must have a:
Device that gives energy to the charged particles constituting the current, such as a battery or a generator
Devices that use current, such as lamps, electric motors, or computers
The connecting wires or transmission lines
The laws that govern how electric circuits behave are Ohm’s Law and Kirchhoff’s rules
Alternating Current vs Direct Current
Alternating Current
A type of electrical current in which the direction of the flow of electrons switches back and forth at regular intervals or cycles
Type of current used in residences and business
From a power plant, generator, alternator etc.
Direct Current
An a electrical current which flows consistently in one direction, from positive to negative terminals
From batteries, fuel cell, solar panel, dynamo etc.
Alternating Current
A simple AC generator consists of a coil of wire rotating in a magnetic field
As one side of the coil moves up through the magnetic field, a potential difference is induced (created) in one direction
As the rotation continues and that side of the coil moves down, the induced potential difference reverses direction
Electrons in the (copper) wire move towards the positive side of the magnet when this in close proximity or away from the negative side when this is in close proximity
Direct Current
Unidirectional flow of current; current only flows in one direction
Voltage and current can vary over time as long as the direction of flow does not change
Different sources but batteries most common
Electrical Current
Flow of charged particles
Results from the flow or movement of electrons
Unit of current = Ampere (Amps) [A]
1 Amp = current which flows when an electric charge of one coulomb passes a given point in one second [Coulomb = measure of electric charge]
For diagnostic radiography exposures = milli Amps (mA)
Voltage
The electrical force between two points that would drive an electric current between these points
The pressure from an electrical circuit’s power source that pushes charged electrons (current) through a conducting loop
The difference in electric potential between two points (potential difference)
Unit of voltage = Volt (V)
1 Volt = energy consumption of 1 joule per electric charge of 1 coloumb [Joule = measure of energy]
For diagnostic radiography exposures = kilo volts (kV)
For therapeutic radiography exposures = mega volts (mV)
