**Solutions: Radioactivity Questions**

**Q1. **

(a)

(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.

N=Z

Scales on graph

**(5 marks) **

(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

**(2 marks) **

(c) The results of electron scattering experiments using different target elements show that

where A is the nucleon number and r_{o} 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 R^{3}, 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.

**(3 marks) **

**(Total 10 marks) **