Question

type the correct answer in the box. round your answer to the nearest thousandth. what is the average atomic mass of the element? an element, x, has two isotopes, x-14 and x-15. use the data in the table to find the average atomic mass of element x.
isotope | atomic mass | abundance (%)
x-14 | 14.003 | 99.636
x-15 | 15.000 | 0.364
the average atomic mass of element x is amu.

Explanation:

Step1: Calculate contribution of X-14

Multiply atomic mass of X-14 by its abundance (in decimal).
$14.003 \times \frac{99.636}{100} = 14.003 \times 0.99636$
$= 13.95239908$

Step2: Calculate contribution of X-15

Multiply atomic mass of X-15 by its abundance (in decimal).
$15.000 \times \frac{0.364}{100} = 15.000 \times 0.00364$
$= 0.0546$

Step3: Sum the contributions

Add the two contributions to get average atomic mass.
$13.95239908 + 0.0546 = 14.00699908$

Step4: Round to nearest thousandth

Round $14.00699908$ to three decimal places.
$14.007$ (since the fourth decimal is 9, which rounds up the third decimal from 6 to 7)

Answer:

14.007