[nursegirl]

Hello everybody I am new and I need help as I said above
Here is my question
A certain isotope of sodium is radioactive and is sometimes used to study blood circulation problems .This isotope has a half of 4.0 days.Beginning with 1000 atoms ,how many of these atoms will be left after:
(a) 8 days?
(b) 16 days?
Hope to read about you soon
Best,

[ifuller]

Check out this website:
http://en.wikipedia.org/wiki/Half-life
Although it is not always best to use wikipedia in this case it seems pretty accurate.

Some of it seems pretty complacated but especially check out the table on the right side of the site. Take note of the percent of material left after a certain number of half-lives.
How many half-lives have passed in both of your examples? If you use that number of half-lives in the table, the right hand column should tell you what percent of the initial number of atoms are left. Hope this helps.

[Borek]

Please read forum rules. Especially parts about trying yourself first and naming threads.