Question

14.calculate the average atomic mass for oxygen. isotope information is provided below. show your work & check your answer against the mass listed on the periodic table.

isotope	natural abundance on earth (%)	atomic mass (amu)
$^{17}\text{o}$	0.04	16.9991
$^{18}\text{o}$	0.20	17.9992

Explanation:

Step1: Convert percentages to decimals

$99.76\% = 0.9976$, $0.04\%=0.0004$, $0.20\% = 0.002$

Step2: Multiply each isotope's mass by its abundance

For $^{16}\text{O}$: $0.9976\times15.9949 = 15.96641224$
For $^{17}\text{O}$: $0.0004\times16.9991=0.00679964$
For $^{18}\text{O}$: $0.002\times17.9992 = 0.0359984$

Step3: Sum the results

$15.96641224+ 0.00679964+0.0359984 = 15.99921028\approx15.999$

Answer:

$15.999$ amu