3.2.1.2 - Unstable and Stable Nuclei Flashcards
What does the nuclear force do?
It overcomes the electrostatic force of repulsion between the protons in the nucleus and keeps the protons and neutrons together.
What kind of effect does the nuclear force have between protons and protons compared to neutrons and protons?
It has the same effect between two protons as it would between two neutrons or a proton and a neutron.
Why does the nuclear force have a short range?
So it only acts within the nucleus.
What is the difference between the range of the strong nuclear force and the range of the electrostatic force?
The range of the strong nuclear is no more than 3-4fm (diameter of a nucleus) while the electrostatic force between two particles has an infinite range.
Why are the nuclei stable?
Because of the huge attractive force the strong force can provide.
How can we estimate the size of the nucleus?
The separation of the nucleons within any nucleus is virtually independent of how many nucleons there are in that nucleus.
Why must the strong nuclear force also be repulsive?
Or else it would crush the nucleus to a point.
How far is the strong nuclear force repulsive up to?
Up to 0.5fm
After what value does the attractive force of the strong nuclear force drop to 0?
3fm
Why will a nucleus emit an alpha or beta decay?
In order for the nucleus to become stable.
What does an alpha particle consists of?
2 protons and 2 neutrons.
What is the relative charge of an alpha particle?
+2
How do we represent alpha particles?
4(on top), 2(on bottom) a.
What happens when an alpha particle is emitted?
The proton number decreases by two and the nucleon number decreases by four.
What is the result of an alpha emission?
The product nucleus belongs to a different element.
When is a beta particle emitted?
In isotopes that are unstable due to being neutron rich.
How can we represent beta emission?
0(on top), -1(on bottom) B
What happens during beta emission?
One of the neutrons in the nucleus changes into a proton. The proton number increases by one, and the nucleon number stays the same.
What else is released during beta decay?
An antineutrino.
What does the antineutrino do?
It carries away some energy and momentum.
How were neutrinos first hypothesised?
Observations of beta decay.
What is a hypothesis?
An untested theory or idea?
How were antineutrinos found?
When they reacted with cadmium nuclei which were in a large tank of water.
What produces neutrinos?
Nuclear reactors, the sun, beta emitting isotopes.
What observation showed that neutrinos may have existed?
During beta emission the energy of particles before and after was less and so didn’t fit the principle of conservation of energy.
What did scientists decide this particle have to be?
Neutral (or charge wouldn’t be conserved) and have a zero or almost zero mass (as it hadn’t been detected).
What are electrostatic forces caused by?
Protons’ electric charges.
What is gravitational force due to?
The masses of the particles.
