# The Naked Scientists Forum

### Author Topic: How do we calculate half life from a graph of isotope abundance?  (Read 5369 times)

#### thegers91

• Jr. Member
• Posts: 19
##### How do we calculate half life from a graph of isotope abundance?
« on: 27/04/2008 10:58:14 »

need some help
« Last Edit: 28/04/2008 10:43:46 by BenV »

#### lightarrow

• Neilep Level Member
• Posts: 4586
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##### Re: How do we calculate half life from a graph of isotope abundance?
« Reply #1 on: 27/04/2008 21:01:15 »

need some help

B 4 days.

Explanation: from the chart it's apparent that 75% of the isotope 200 has transformed in the isotope 196 (it couldn't be the opposite, that is 25% of the 196 into the 200, because it can't gain mass). Half-life means that after that time half of the initial isotope decays, so an half-life of 4 days means that 50% of the initial quantity of 200 has transfomed into 196. So in 4 days we are left with 50% of the 200. After other 4 days this amount will be halfed again, so it will remain 25%. In conclusion: after 8 days will remain 25% of the initial isotope 200 and the rest 75% has become the isotope 196, as results from the chart.

#### The Naked Scientists Forum

##### Re: How do we calculate half life from a graph of isotope abundance?
« Reply #1 on: 27/04/2008 21:01:15 »