a) (i) Thorium is a radioactive element - Edexcel - GCSE Physics - Question 6 - 2017 - Paper 1

The initial activity of a radioactive sample is directly related to its decay rate and the number of atoms present. Since both samples (thorium and radium) start with the same number of atoms, their initial activities can be compared using their half-lives. The activity of a radioactive substance can be calculated using the formula:

$A = \frac{N}{t_{1/2}}$

where (A) is the activity, (N) is the number of undecayed nuclei, and (t_{1/2}) is the half-life. Therefore, the sample with a shorter half-life, radium, will have a greater initial activity compared to thorium.

Alpha radiation is:

X B is highly ionising

Today, there are laws about how radioactive materials can be used because:

X C we understand more about the effects of radiation.

Using an isotope of thorium in toothpaste poses significant health risks due to its radioactive nature. The decay of thorium produces alpha radiation, which, while having low penetration ability, can cause severe damage if ingested or if it gets into the body through wounds. Long-term exposure to radioactive materials can lead to increased risks of cancer and other health issues because alpha particles can cause ionization in cells, potentially leading to mutations. Regulations are now in place due to a better understanding of the harmful effects of radiation, emphasizing the dangers of using radioactive substances in everyday products, such as toothpaste.