Answer:
Therefore 21.09 gram of the element remains after 17 years.
Step-by-step explanation:
The decay rate is proportional to the number of nuclei.
Integrating both sides
Initially N= , when t=0
The equation becomes
N= Remaining mass after t time
= initial mass of the sample
= decay constant
Given that, every 12 years the mass of a sample of a the element is one third of the initial mass.
Here, , t= 12 years
[ ]
[ and ]
The equation becomes
Given that, the initial amount and t =17
gram
Therefore 21.09 gram of the element remains after 17 years.