Stable And Unstable Nuclei Flashcards
What are the forces that act in the nucleus?
Electromagnetic
Gravitational
Strong nuclear
What does the electromagnetic force do?
Causes positively charged protons in the nucleus to repel each other
What does the gravitational force do?
Causes all the nucleons in the nucleus to attract each other due to their mass
What does the strong nuclear force do?
Holds the nucleus together
Why is there a strong nuclear force?
The repulsion from the electromagnetic force is much bigger than the gravitational attraction so the nucleons would fly apart without the strong nuclear force
Is the strong nuclear force stronger than the electromagnetic force?
Yes
What is the range of the string nuclear force?
Very short
A few femtometres
At very small separations, is the strong nuclear force attractive or repulsive?
Repulsive
When is the strong nuclear force repulsive?
For very small separations of nucleons
Less than about 0.5fm
When does the strong nuclear force become attractive?
As nucleon separation increases past about 0.5fm
When does the strong nuclear force reach maximum attractive value and then falls rapidly towards 0?
After about 3fm
How far does the electromagnetic repulsive force extend over?
Much larger range than the strong nuclear force
What is nuclear decay?
When unstable nuclei will emit particles to become more stable
When does alpha decay happen?
In very big atoms
Why does alpha decay happen?
The nuclei of the atoms are too big for the strong nuclear force to keep them stable
What happens to the atoms during alpha decay?
What happens to the proton and nucleon number~?
They emit an alpha particle
Proton number decreases by 2
Nucleon number decreases by 4
What is the range of alpha particles?
Very short range (only a few cm in air)
How can alpha decay be seen?
By observing the tracks left by alpha particles in a cloud chamber
OR
Using a Geiger/spark counter
What do Geiger and Spark counters measure?
Amount of ionising radiation
What is beta minus decay?
Emission of an electron from the nucleus along with an antineutrino particle
When does beta minus decay happen?
In isotopes that are ‘neutron rich’
What happens when a nucleus ejects a beta particle?
1 of the neutrons is changed into a proton
Proton number increases by 1
Nucleon number stays the same
What does the antineutrino particle released in beta minus decay carry away?
Some energy and momentum
How far can beta particles travel in air?
Several metres
