Phsyics Atomic Structure Flashcards
What is an Isotope ?
Isotopes are atoms of the same element with the same atomic (proton) number but with different Atomic Masses
What is the typical radius of an atom?
1 × 10‐¹⁰ meters
What did Dalton discover in 1800?
He said that everything was made of tiny spheres that could not be divided
What did JJ Thompson discover in 1897?
He discovered the electron
What did JJ Thompson form after discovering the electron ?
The plum pudding model
What did Rutheford discover in 1911 ?
He realised that most of the atom was empty space through the gold foil experiment
What does most alpha particles going straight throught tell us?
That most of the atom is empty space
What does some alpha particles being slightly deflected tell us ?
That the nucleus must be positively charged
What does few alpha particles being deflected at 90° tell us ?
That the nucleus contained most of the mass
What does the 1913 Rutherford Model tell us ?
That there is a positive nucleus at the centre of the at and negative electrons around it
Who produced the final model of the atom?
Bohr in 1913
What is Radioactive Decay ?
This is where some unstable nuclei gives out radiation to become more stable
What is activity ?
Activity is the rate at which a source of unstable nuclei decays ; a sample with high activity has a fast rate of decay
What is count rate ?
The number of decays recorded by a detector per second
What are the properties of Alpha decay ?
Highly Ionising
Weakly Penetrating
( 5cm , air )
What are the properties of Beta decay ?
Medium Ionising
Medium Penetration
( 50cm of air , a sheet of paper )
What are the properties of Gamma Radiation ?
Low Ionising
Highly Penetration
( very far in air , few cm of lead )
What does Alpha decay do to the element ?
The Mass Number is minused by 4 and the Atomic Number is minused by 2
What happens to the element in beta decay ?
Nothing to the Mass Number but the Atomic Number is added by 1
What is Half-life ?
The time it takes for half the nuclei in a sample to decay
What does a short half-life show ?
That it decays quickly with high activity
What does a long half-life show ?
It decays quickly with low activity
How is a medical tracer used ?
It is a half life of a few hours
It is a short half-life so it can stop any danger
It is gamma based so it can pass through the body tissue without being absorbed
How is it used in Medical Implants ?
The implant is alpha/beta as they need high ionizing power and low penetration power
Their will be a short half-life so it can decay quickly with high activity
How is it used in Radiotherapy and Sterilisation ?
It is gamma for low ionizing power but high penetration power so it can move through the passage quicker
What is Nuclear Fission ?
It is the splitting of a large nucleus into 2 smaller nuclei
What happens in Nuclear Fission ?
The unstable Nuclei absorbs a neutron that splits into 2 smaller nuclei these then emit 2 or 3 other neutrons
What happens during Nucelar Fission ?
Energy is released in the form of Gamma Ray’s
The neutron may collide with another radioactive nucleus
This nucleus absorbs the neutron and becomes unstable
This nucleus the splits again releasing another neutron producing more energy
What happens if the Chain reaction is not controlled ?
It will increase in exponential rate
What is Nuclear Fusion ?
This is when 2 small nuclei fuse to form a heavier nucleus releasing lots of energy
What does Nuclear Fusion require ?
It requires massive amounts of energy and pressure
Where does Nuclear Fusion occur ?
In the stars naturally or the sun
What else does Nuclear Fusion require ?
High Temperature
What are some Natural types of Background radiation ?
Radon Gas
Food + Drink
Cosmic Ray’s
Buildings
What are some Artificial types of Radiation ?
Nuclear power plants + waste
Nuclear weapons testing
Medical testing
