Topic 4 (Atomic Structure) PHYSICS Flashcards
What is the plum pudding model
A ball of positive charge with electrons stuck in it
What was Rutherfords nuclear model
A small positive nucleus with a cloud of negative electrons. Most of the atom was empty space
What was Bohr’s nuclear model
It suggested that there was still a small positive nucleus, but the electrons surrounding it, orbited in rings
Number protons equals what
Number electrons
What is an isotope
An isotope is a different form of the same element they have the same number of protons but a different number of neutrons
What are alpha particles
Alpha particles are helium nuclei. They get stopped by a few cm of air but they are highly ionising
What are beta particles
Beta particles are fast moving electrons.
They get stopped by thin sheets of aluminium (5mm) and they are moderately ionising.
What are gamma rays
Waves of electromagnetic radiation they travel long distances in the air they are weakly ionising compared with alpha and beta particles. They are absorbed by thick sheets of lead or concrete walls (3+ metres)
What is the mass number for an alpha particle
4
What is the mass number for a beta particle
0
What is the atomic number for an alpha particle
4
What is the atomic number for a beta particle
-1
What is a half life
The amount of time it takes for the number of radioactive nuclei in an isotope to halve
How can gamma rays be used in the medical world
Since gamma rays are weakly ionising and have extremely short half life’s they can be used to kill the cancer cells whilst not damaging normal cells. However sometimes if to much radiation enters the body it can lead to mutant cells which divide uncontrollably which is just more cancer. This is why every medical situation has to look at risks and rewards
What is nuclear fission
Nuclear fission is the splitting of large unstable nuclei to release energy. When a neutron is shot into an unstable atom it is absorbed, this large nucleus then splits releasing two or three more neutrons which are absorbed by other unstable atoms. This causes a large chain reaction