Atomic Structure Flashcards
When might the energy level of an electron change?
When an atom emits or absorbs electromagnetic radiation.
What is an isotope?
Atoms of the same element which have different numbers of neutrons.
Who discovered electrons and when?
J. J. Thompson in 1897.
Describe the plum pudding model.
A large ball of positive charge, scattered with negative electrons.
When did Rutherford’s scattering experiment take place?
1905.
What did the results of Rutherford’s scattering experiment tell us?
The mass of the atom was concentrated in a central, positively-charged nucleus.
Electrons surrounded this nucleus.
What developments to the model of the atom did Neils Bohr suggest?
Electrons orbit the nucleus at specific distances.
In what year did James Chadwick discover the neutron?
1932.
What was Chadwick’s model called?
The nuclear model.
Why does radiation happen?
So that an unstable nucleus may become more stable.
What is the activity of a radioactive source?
The rate in which it decays.
What is one becquerel (Bq) the equivalent of?
One decay per second.
What type of radiation can be stopped by paper?
Alpha.
What type of radiation can be stopped by a thin sheet of aluminium?
Beta.
What type of radiation can only be stopped by a thick sheet of lead?
Gamma.
What does ionising radiation mean?
It is capable of knocking electrons from atoms.
Which types of ionising radiation are ejected from the nucleus?
Alpha, beta.
Which types of ionising radiation are emitted from the nucleus?
Gamma.
What is radioactive contamination?
The unwanted presence of materials containing radioactive atoms on other materials.
What is irradiation?
The process of exposing an object to nuclear radiation.
What is the half-life of a radioactive isotope?
The average time it takes for half of the nuclei to decay/the time taken for the count rate to fall by half of its original value.
What is an alpha particle represented as?
4
He
2
What is a beta particle represented as?
0
e
-1
