How do you determine the total mass of an original 28.0-milligram sample of Po-210 that remains unchanged after 414 days?

1 Answer
Jun 12, 2017

Answer:

Given the 138.4 day half-life of the radioisotope #3.5*mg# of #""^210Po# will remain.

Explanation:

Given the boundary conditions of the problem it was SPECIFIED that the mass of #""^210Po# remained unchanged. I acknowledge, however, that this is a radioactive decay problem, and #""^210Po# is a screaming hot isotope and #alpha-"emitter"# with a half-life of 138.4 days; these data SHOULD have been supplied with the problem.

And so your polonium isotope has experienced 3 half-lives.........And there is thus #(1/2)^3=1/8# of the original mass, i.e. #3.5*mg#.

Note that I think this was the first radioisotope isolated by Marie Curie who named it after her native Poland.