Atomic structure Flashcards
(25 cards)
Dalton model
Solid spheres
plum pudding model
electrons in a massive ball of positive charge
alpha scattering experiment
positive alpha particles fired at 1 atom thick gold sheet
most went straight through
some were deflected
this shows that the atom is mostly empty space, yet they contain a positively charged mass in the centre (nucleus)
What did neils bohr find out
electrons fly in shells
When were protons discovered
1920
What did james chadwick discover
Showed that the nucleus also contained neutrons
The nuclei of some isotopes are ______. These give off _____ as they ________. This is called ______.
unstable, radiation, change to become more stable. Radioactive decay
Activity is the rate at which _____ and the measured in _______.
radioactive decay happens, becquerels (Bq)
Radioactive decay is measured using a ______.
Geiger counter
All radiation _____
Ionises
What is an ion?
A charged particle made when atoms gains or lose electrons
What is an alpha particle made of
2 protons and 2 neutrons
Properties of alpha particles
Are very ionising
Are not very penetrating
Have a very short range in air
Air deflected by an EM field
Can be stopped by paper
What is alpha decay
a type of radioactive decay where a nucleus emits 2 protons and 2 neutrons
Properties of beta particles
Are less ionising
Are more penetrating
Have a medium range in air
Are deflected by an EM field
Can be stopped with aluminium foil
What is beta decay
A neutron changes into a proton and fast moving electron (beta particle)
Properties of gamma radiation
Not a particle
Not very ionising
Highly penetrating
Huge range in air
Not deflected by an EM field
Can be stopped by thick lead
What is half life
the time taken for the count-rate to decrease by half (or for half the number of atoms to decay)
What is contamination
Unwanted presence of radioactive ions
Irradiation
Exposure to radiation
Uses of radioactive isotopes
Radioactive tracers:
Within body
Short half life
Detected using PET scanner
Radiation therapy:
Kills cancer cells
uses a focussed gamma ray gun that rotates
What is nuclear fission
The splitting of a large unstable nucleus by firing a neutron at it
How is a nuclear reactor controlled
Using boron control rods, moving up or down
What is nuclear fusion
Fusion is the joining of two atomic nuclei to create a larger one
Found in stars
In hydrogen bombs
