Question

Po-218 is an alpha emitter with a half-life of 3.0 minutes. If a sample contains 69 mg of Po-218, how many alpha emissions would occur in 6.0 minutes?

the answer has to be _________a emmisions (which I have no idea what it means)
and I use a chart thing with amount, #H-L, and time passed as the collums.

Answer 1

I would do something like this.
(Number of half lives = 6/3 = 2.)
2ⁿn = 2^6/3 = 2² = 4 and
69 mg/4 = 17.25 Po atoms remain. The mass that emitted must be 69mg-17.25mg = 51.75 mg or 0.05175 grams.
I would change that to moles (moles = grams/molar mass) and remember that 1 mole of atoms contains 6.022 x 10^23 atoms.
So moles x 6.022 x 10^23 = ??number of alpha emissions.