Decay Chains

To be able to determine radioactive decay chains

An exam question…Potassium decays into argon. The half life of potassium is 1.3 billion years. A sample of rock from Mars is found to contain three argon atoms for every atom of potassium. How old is the rock?

(3 marks)

The rock must be 2 half lives old – 2.6 billion years

Decay chains

If Uranium 238 decays via alpha emission, what will the ‘daughter’ atom be?

How can we show this?

What about if C 14 decays via beta emission?

Remember beta emission causes a neutron to turn into a proton.Alpha emission ejects 2 P and 2 N.

Try these ones

1. Fr 225 decays via beta emission2. Pu 239 decays via alpha emission3. F 20 decays via beta emission4. Ne 20 decays via alpha emission

If mercury underwent beta emission, then the daughter atom underwent alpha emission, what would the product be?

An exam question…

Potassium decays into argon. The half life of potassium is 1.3 billion years. A sample of rock from Mars is found to contain three argon atoms for every atom of potassium. How old is the rock?

(3 marks)

The rock must be 2 half lives old – 2.6 billion years