Compute the mass in grams of a sample of amercium containing six atoms?

Question

this is what i did

6 atoms Am x (243g/atom) = 1.46 x 10^3 g

book's answer: 2.42 x 10^-21

Answer 1

The atomic weight of Am is 243 g / 6.02 x 10^23 atoms.  Divide by Avagadro's number and then multiply by the atomic mass and you'll get the book's answer.

Answer 2

6 atoms AM

6.022e23 atoms AM in one mole AM

1 mole AM equals 243 g

dimensional analysis works best.

(6 atoms AM/1)(1 mole AM/6.022e23 atoms AM)(243 g AM/1 mole AM)

Multiply what is in the first part of each parenthesis and then divide it by the bottom you should get what I got...2.42e-21

If you are a little confused by my methods the calculations i did were (6)(243)/6.022e23