Readioactivity Flashcards
(15 cards)
Alpha radiation
Stoped by paper
Has the greatest ionising power
Beta radiation
Went through paper
It has less ionising power than alpha but more than gamma
Gamma radiation
Which is even more penetrating that beta radiation
Least ionising power
Alpha radiation charge
Positive
Radioactive substance
Contains an unstable nuclei that becomes stable by emitting radiation
Ernest Rutherford discovered:
Most alpha particles went straight through
No. Of alpha particles which deflected decreased as the angle of deflection increased
About 1 in every 10000 alpha particles were deflected by more than 90°
Where most of the mass of the atom was located
Plum pudding model and nuclear model in terms of the Rutherford experiment
The plum pudding model could not explain why some alpha particles scattered through large angles. The nuclear model of the atom was able to correctly explain this as there was a small positively charged nucleus in the centre where most of the atoms mass was located. (High density)
Atomic number
Number of protons
Mass number
Protons and neutrons
Isotopes
Are atoms of the same element with different numbers of neutrons.
Alpha emission
Alpha particle is made up of 2 protons and 2 neutrons.
Relative mass is 4 and its relative charge is +2
Represented by the symbol 4/2
Atomic number goes down by 2
And the mass number goes down by 4
example of alpha emission:Thorium isotope decaying Th 228/90
Ra 224/88
Beta emission
It has a negative charge Relative mass of a beta particle is 0 And the relative charge is -1 Represented as 0/-1 Atomic number of nucleus goes up by 1 And the mass number is unchanged because neutron changes into proton
Example of beta emission: potassium isotope 40/19K
Turns into 40/20Ca a calcium Isotope
Half life of a radioactive substance
Is the average time it takes for the number of nuclei of the isotope in a sample to halve
