1.2 stable and unstable nuclei

What defines a stable isotope?

Having nuclei that doesn’t disintegrate

What force holds together a stable nucleus?

Strong nuclear force

What is the SNF’s role within the nucleus?

The strong nuclear force overcomes the electrostatic force of repulsion between the protons in the nucleus and keeps the protons and neutrons together

What is the range of the strong nuclear force?

The SNF has a range of no more than 3 femtometres.

What is the SNF’s range for attraction?

0.5fm - 3fm

What is the SNF’s range for repulsion?

Separations lower than 0.5fm

What is the purpose of the strong nuclear force being attractive and repulsive?

Attractive: to overcome electrostatic forces of repulsion between the positive protons

Repulsive: prevents protons and neutrons being pushed into each other

What are the 3 types of naturally occurring radiation?

Alpha, beta, gamma

In beta decay, a beta particle is emitted. However, there is another particle that also is emitted during the process. What is the name of this particle?

Antineutrino

In what situation is gamma emitted from a nucleus?

When the nucleus has too much energy

What is the need for neutrinos?

When the energy spectrum of beta particles was first measured, it was found that beta particles were released with kinetic energies up to a maximum that depended on the isotope.

This puzzled scientists as to why the energy of the B- particles varied up to a maximum, when each unstable nucleus lost a certain amount of energy in the process.

So the existence of the neutrino was hypothesised to account for conservation of energy in beta decay

(B particle with non maximum energy + antineutrino = maximum energy → energy has been conserved)

Why was the existence of the neutrino hypothesised?

To account for conservation of energy in beta decay

At what distance is the strong nuclear force the most attractive?

1.5 fm