Solutions: Radioactivity Questions
(i) Sketch a graph to show how the neutron number, N, varies with the proton number, Z, for naturally occurring stable nuclei over the range Z = 0 to Z = 90. Show values of N and Z on the axes of your graph and draw the N = Z line.
(ii) On your graph mark points, one for each, to indicate the position of an unstable nuclide which would be likely to be an emitter, labelling it A, a emitter, labelling it B.
Scales on graph
(b) State the changes in N and Z which are produced in the emission of
(i) an particle,
N decreases by 2; Z decreases by 2
(ii) a particle.
N decreases by 1; Z increases by 1
(c) The results of electron scattering experiments using different target elements show that
where A is the nucleon number and ro is a constant. Use this equation to show that the density of a nucleus is independent of its mass.
Denisty = mass/molume = m/V
Now, mass (m) is proportional to A
and volume (V) is proportional to R3, from the equation above we see that R is proportional to the cube root of A; therefore Volume V is proportional to A
Therefore density is proportional to A/A = 1.
i.e. density is independent of A.
(Total 10 marks)