P4 - Atomic Structure Flashcards
What was the first model of the atom?
Tiny sphere that can’t be broken up.
What was the second model of the atom?
PLUM PUDDING MODEL
Sphere of positive charge with negative electrons stuck in it.
What was developed after the plum pudding model?
The alpha scattering experiment. Alpha particles thrown at gold foil and a few deflected back but most passed through.
This shower most of the mass of an atom is concentrated at the centre ( nucleus).
And nucleus is positively charged
What was the third model of the atom?
NUCLEAR MODEL
positively charged nucleus surrounded by could of negative electrons.
What was developed after the nuclear model?
Niels Bohr’s theoretical calculations( that agreed with experimental data).
What was the last the fourth model of the atom?
BOHR MODEL
electrons orbit the nucleus at certain distances
What is an isotope?
Atoms with the same number of protons but different number of neutrons.
ALPHA
Absorbed by
Range in air
Ionising power
Example of use
Sheet of paper
Few centimetres
Strong
Smoke detector
BETA
Absorbed by
Range in air
Ionising power
Example of use
Sheet of aluminium
Few metres
Moderate
Material thickness testing
GAMMA
Absorbed by
Range in air
Ionising power
Example of use
Thick sheets of lead
Longer distances
Weak
Medical tracers
What is radioactive contamination?
Getting unwanted radioactive aroma onto or into an object
What is irradiation?
The exposure of an object to nuclear radiation( doesn’t make the object radioactive).
What is half life?
The time taken for the number of nuclei of an isotope in a sample to halve.
What is the risk of radiation? What can happen? (4)
- Radiation can enter a living cell, ionising atoms within it
- Cell can be killed
- Cell can be damaged
- Damaged cell can multiply and become cancer
What are 2 ways ionising radiation is used in radiotherapy to kill cancer cells?
- Gamma sources from outside body directed at cancer cells.
- Beta sources used in medical implants put inside body next to cancer cells.
