Question

Magnesium has three naturally occurring isotopes: 24Mg (79%), 25Mg (10%), and 26Mg (11%). What is the relative atomic mass of magnesium to one decimal place?

a. 24.4
b. 24.6
c. 24.9
d. 25.2

Answer 1

The average atomic mass of magnesium is 24.3 amu.

Step-by-step explanation:

The average atomic mass of magnesium can be calculated by taking the weighted average of the mass of each isotope, based on its percent abundance. The formula for calculating average atomic mass is:

Average atomic mass = (% abundance of isotope 1 * mass of isotope 1) + (% abundance of isotope 2 * mass of isotope 2) + (% abundance of isotope 3 * mass of isotope 3)

Using the given percent abundances and masses of the three magnesium isotopes, we can calculate:

(0.787 * 24.31 amu) + (0.10 * 25.32 amu) + (0.11 * 26.93 amu) = 24.31 amu

Therefore, the relative atomic mass of magnesium is 24.3 amu.