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GCSE Questions: Radioactivity

Q15. Polonium-210 ( ) is a radioactive isotope that decays by emitting alpha radiation.

(a) Complete the decay equation for polonium-210

[2 marks]

(b) Explain why contamination of the inside of the human body by a radioactive material that emits alpha radiation is highly dangerous.

Alpha radiation is highly ionising causing an increased risk of cancer or organ failure or radiation sickness/poisoning or mutation of genes/DNA or damage to cells/tissues/organs.

It remains a serious hazard until the radioactive material is removed/excreted or all absorbed by the body or the activity of radioactive material approaches background radiation levels.

[3 marks]

(c) A sample of polonium-210 was left for 414 days.

After this time it had a mass of 1.45 × 10-4 g

The half-life of polonium-210 is 138 days.

Calculate the initial mass of the sample.

414/138 = 3

So it was left for three half lives.

Let m be the original mass

After 1 half life there would be ½ x m

After 2 half lives therewould be ½ x ½ x m

So, after 3 half lives there would be ½ x ½ x ½ x m

m/23 = 1.45 x 10-4

m = 8 x 1.45 x 10-4

m = 1.16 x 10-3 g

[3 marks]

(Total 8 marks)