P4 Atomic Structure Flashcards
What did J.J. Thomson discover?
He discovered electrons and proposed that atoms were positively charged spheres with electrons in them like a plum pudding
What did Rutherford discover?
He fired alpha particles at a thin gold foil with most passing straight through, some being slightly deflected and few deflected backwards. He then realised that most of the mass must be concentrated at the centre in a tiny, positively charged nucleus
What did Bohr do?
He proved that electrons orbited the nucleus at certain distances
What did Chadwick do?
He proved the existence of the neutron
What is an isotope?
A different form of the same element with the same number of protons but a different number of neutrons
What is an alpha particle made of?
2 neutrons and 2 protons (helium nucleus)
How penetrating is an alpha particle?
Low
How ionising is an alpha particle?
High
What is a beta particle made of?
A high speed electron
How penetrating is a beta particle?
Medium
How ionising is a beta particle?
Medium
What is a gamma radiation made of?
A gamma ray
How penetrating is a gamma ray?
High
How ionising is a gamma ray?
Low
What is half-life?
The time taken for the activity of a radioactive source to halve
What is radioactive activity measured in?
Becquerels (Bq)
What is background radiation?
Radiation that is around us all the time
What are some sources of background radiation?
Natural: rocks, cosmic rays, food
Human activity: Radioactive waste, fallout
What is irradiation?
Exposure to a radioactive source
What is contamination?
A radioactive source or atoms get onto an object
How do tracers work?
Gamma radiation is injected into the body, which is then followed around the body using an external detector
How are patients treated with radiotherapy?
Radiation is carefully directed and at the right dosage to kill the cancer cells without damaging too many normal cells
What are the processes for nuclear fission?
- A neutron collides with an unstable nucleus, causing it to split and form two or three lighter nuclei and two or three neutrons
- This releases energy used to heat water to turn turbines and generators
What are the processes of nuclear fusion?
- Two light nuclei collide at high speed to fuse and create a larger nucleus
- Some of the mass of the lighter nuclei is converted to energy and released
- This releases energy which is used to heat water and turn turbines and generators
