Nuclear Physics Flashcards
3 isotopes of hydrogen
(1 1) Protium
(1 2) Deuterium
(1e 3) Tritium
Fissile material
Material that can undergo the fission reaction
The Rutherford model
A gold leaf experiment conducted in 1909 by Hans Geiger and Ernest Marsden in which alpha particles were fired at a thin gold leaf (1000 atoms thick). About 1/8000 particles hit the very small, surrounded mostly by empty space, nucleus(containing most of the mass) and were deflected due to the like charge of the alpha particles and protons in the nucleus.
The atoms far away would be unaffected by the forces and continue in a straight path, those closer would be deflected, and closer would completely turn around
Atom
Smallest unit of matter that still retains the chemical properties of its elements
Structure of an atom
Consists of a central, positive nucleus containing protons and neutrons, orbited by shells/orbitals carrying negative electrons.
What is this referred to as
A=
X=
Z=
Nucleic notation
A = (big no.) atomic mass/nucleon no.
X= element symbol
Z= proton/atomic mass
Isotopes
Atoms with the same number of protons but different mass numbers. Most radioactive elements exist as isotopes
What happens during nuclear processes
The proton and atomic mass number are conserved
The H represents an alpha particle and nuclear radiation
What prevents electrons from falling into the nucleus
Their speed
Proton number
Number of protons in a nucleus
Proton charge
1.6x10*-19
Nucleon number
Number of protons and neutrons in an atomic nucleus
Isotope
Same proton number different mass number
Nuclide
Species of nucleus having particular values of proton and nucleon numbet
2 isotopes of helium
3/2 -rare
4/2 - commonest
What does it mean when an isotope is unstable
It undergoes radioactive decay, emitting radiation as it changes from one element to another
Nuclear fission
When a heavier nucleus divides into 2 smaller ones. Induced by an introduction of a neutron as the neutron has no charge and is not deflected by the positively charged protons in the nucleus.
Radioactive decay
The decay of a radioactive substance when its atomic nuclei emit radiation (to become stable?)
Nuclear fusion
The process by which energy is released by joining together 2 small light nuclei to form a new heavier nucleus
In the sun: (When 2 energetic hydrogen atoms collide and fuse to form a helium atom)
Contaminated
When an object has acquired some unwanted radioactive substance
Irritated
When an object has been exposed to radiation
Background radiation
Radiation from the environment which we are exposed to all the time
Sources that make a significant contribution to background radiation (4)
Radon gas (and thoron) in air (main)
Cosmic rays
Food and drink
Rocks and buildings
How can ionising nuclear radiation be measured
With a detector connected to a counter (geigercounter)
Sources of artificial radiation (3)
Medical
Fallout from weapons test
Air travel, TV sets
Describe the emission of radiation from a nucleus
Spontaneous and random in direction
What does an atom of a radioactive substance emit
Either an alpha or beta particle
Emits energy in the form of a gamma ray (sometimes same time,sometimes later)
How fast gamma rays travel
At the speed of light
Alpha nature
Alpha radiation has a high power of ionisation but low penetration
Ionisation
When a particle becomes radioactively charged by losing/gaining electrons
Ionising radiation
Radiation that causes ionisation
High ionising, low pentrating
Alpha (sheet of tissue paper)
Low ionising high penetrating (aluminium stops it)
Gamma
Low ionising, high penetration (lead needed to stop it_
Gamma rays
Penetrating power
How far radiation can penetrate into different materials
deflection of α-particles, β-particles
and γ-radiation in magnetic
fields
Alpha deflected
Beta deflected more in the opposite direction
Gamma not deflected
deflection of α-particles, β-particles
and γ-radiation in electric fields
Alpha is positively charged
Beta is negatively charged
Gamma is neutral
Effects of ionising nuclear radiations
Death in cell due to ionisation
Damage to nucleus results in control mechanisms being broken down and uncontrollable division (tumor + cancer)
Damage DNA if affected cell is a gamete, mutation passed through generations as the egg may not develop at all, or form a genetic disorder
Why may isotopes of an element be radioactive
Due to an excess of neutrons in the nucleus an/or the nucleus being too heavy
Radioactive decay
Change in an unstable nucleus that can result in the spontaneous and random emission of alpha/beta particles or gamma rays.
What happens to the nucleus during alpha or beta decay
It changes to that of a different element
Half life
Time taken for half the nuclei of the isotope to decay
Radioactive tracing
Technique that uses a radioactive substance to trace the flow of liquid or gas/ to find the position of cancerous tissue in the body
effect of α-decay, β-decay and γ-emissions on the nucleus
Increase in stability and reduction in the amount of excess neutrons
Neutron -> proton + electron
Beta decay
Decay of a radioactive nucleus by emission of a beta-particle (used in carbon dating)
how radioactive materials are moved,
used and stored in a safe way
Reduce exposure time
Increase distance between source and living tissue
Use shield to absorb radiation
Gloves and tongs
Stored in a container that absorbs as much radiation as possible
Uses of radioactivity (5)
Thickness control - beta radiation (gm tubes)
Medical (diagnosing and treating cancer and X-rays) - gamma rays IODINE 123
House hold fire alarms - alpha (knows when alpha is being blocked by smoke)
Irritating food to kill bacteria (gamma)
Sterilisation of equipment - gamma rays
