Topic P4 Flashcards
What is the structure of the atom and how did it develop further
Tiny sphere that can’t be broken up
–> Electron discovery
What is the structure of the plum pudding model and how did it develop further
Sphere of positive charge with negative electrons stuck in it
–> Alpha scattering experiment
What is the structure of the Nuclear model and how did it develop further
Positively charged nucleus surrounded by cloud of negative electrons
–> Niels Bohr’s theoretical calculations agreed with experimental data
What is the structure of the Bohr model1
Electrons orbit the nucleus at certain distances
How did the Bohr model develop
It was found the nucleus could be split into smaller particles
1) The positive proton was found
2) 20 years later nuetrons were proved by James Chadwick
What is the alpha particle experiment
Multiple alpha particles flew at a thin piece of gold foil and most passed through but a few deflected back
This showed:
- Most of the mass of the atom was concentrated at the centre (nuckeus)
- Nucleus is positively charged
How do electrons move between energy levels
Electrons can absorb EM radiation to move to higher energy levels
or Electrons can emit EM radiation to move to lower energy levels
What is the radius of the atom
radius = 1 x 10^-10 m
What is an isotope
An isotope are atoms with the same number of protons but a different number of neutrons
What is the mass number
The mass number is the top number
consists of the total number of protons and neutrons in an atom
What is the atomic number
The atomic number is the bottom number and it has number of protons in the nucleus
number of protons = number of electrons
- shows the charge of the nucleus
What is radioactive decay
When an unstable nucleus decays into another element and gives out radiation to become more stable
What is ionising radiation
Radiation that knocks electrons off of atoms, creating positive ions
what do unstable nuclei do
Unstable nuclei can also release neutrons when they decay
What is in an alpha particle
2 neutrons
2 protons
- called a helium nucleus
what are alpha particles absorbed by
sheet of paper
alpha particle range in air
few cm
how ionising is an alpha particle
very strong (most ionising)
When are alpha particles used
In smoke detectors
What is in a beta particle
fast moving electrons from nucleus
What are beta particles absorbed by
Sheet of aliminuim
beta particle range in air
few metres
ioising power of beta particle
Moderately powerful
When are beta particles used
Material thickness testing
What is gamma particles made of
electromagnetic radiation from nucleus
gamma particles absorbed by
Thick sheets of lead
gamma particle range in air
Longer distances
gamma particles ionising power
weak - least ionising
Gamma particle exmaple of use
Medical tracers
What happens to the atomic and mass number during alpha decay
mass number decreases
atomic number decreases
What happens to the atomic and mass number during beta decay
mass number stays the same
atomic number increases
What happens to the atomic and mass number during gamma decay
Mass number and atomic number stay the same
What does activity mean
The rate at which a source decays
measured in becquerels (bq)
What does count rate mean
The number of radiation counts reaching a detector per second
What measures count rate
A Geiger-Muller tube and counter
What is radioactive contamination
Getting unwanted radioactive atoms onto or into an object
What does irradiation mean
The exposure of an object to nuclear radiation (doesn’t make the object radioactive)
What are 3 precautions to protect against irradtiation
1) Keep sources in lead-lined boxes
2) Stand behind barriers or be in a different room to the source
3) Handle sources with remote controlled arms
Is radioactive decay random - TRUE/FALSE
TRUE
What is a half life
Time taken for the number of nuclei of an isotope in a sample to halve
How to work out half life on graph
look at video
Which are the most dangerous radiation particles to get in your body
most = alpha particle least = gamma particle
What is the most dangerouse radioactive particle to get outside your body
Most = gamma least = alpha
What is the risk of radiation
1) radiation can enter a living cell, ionising atoms within it
2) cells can be damaged and can multiply and become cancer
or
2) Cells can be killed
