Isotope	Protons	Neutrons	Electrons
Ga-67	31	??	??
Ga-69	??	38	??
Ga-71	??	??	31

Gallium (Ga) is an element that exists as numerous isotopes, some of which are radioactive.

i.Complete Table 1 for three of the isotopes of gallium.

Explain why Ga-67 is suitable for use in medical diagnostics.

iv.If the dose rate from a sample of Ga-67 was found to be 0.052mSv per hour at 1.1metres, calculate the dose rate at 3.5 metres. Show your calculations. Give your answer to two significant figures.