1. About how many carbon-14 atoms from a sample of 800 C-14 atoms will remain after 2.0 half-lives? (divide # by 2 for each half-life) 2. About how many N-14 atoms will be present from a sample of 800 C-14 atoms after 2.0 half-lives? (800- Answer to #4)

3. 100 C-14 atoms remain from a sample of 1600 C-14 atoms.

a. How many half-lives have passed? (how many times did you divide 1600 by 2 to get to 100?) i. e. 1600/2 = 800/2=400 etc...

b. How much time has passed? (The half-life of C-14 is 5730 years) (# of half-lives x 5730)