Describe the nuclear reaction shown and identify the isotope with the longest half-life and calculate the relative atomic mass of uranium.

Relative atomic mass = $\sum (\text{isotope mass} \times \text{abundance})$

The relative atomic mass of uranium is $\boxed{234.1156}$.

4. (b) (iii)

4. (b) (iv)
One use of radioactive isotopes in the paper industry is to $\boxed{\text{measure and control the thickness of paper}}$.

5. (a)

A particle with mass number 0 and atomic number -1 is a beta particle ($^{0}_{-1}e$).

5. (b) (i)

The value is approximately $5.7 \times 10^3$ years.
The half-life of carbon-14 from the graph is $\boxed{5.7 \times 10^3 \text{ years}}$.