Question

Magnesium has three naturally occurring isotopes with masses of 23.99 amu, 24.99 amu, and 25.98 amu and natural abundances of 78.99%, 10.00%, and 11.01%, respectively. Calculate the atomic mass of magnesium

Answer 1

Answer: 24.309

Explanation:

Isotope A:

Mass number = 23.99 amu

Abundance = 78.99%

Isotope B:

Mass number = 24.99 amu

Abundance = 10.00%

Isotope C:

Mass number = 25.98 amu

Abundance = 11.01%

To find the atomic Mass of magnesium, we must add the product of the mass number and abundance of each of the isotopes. In doing so, we have:

Let M1 and A be the mass number and the abundance for isotope A.

Let M2 and B be the mass number and the abundance of isotope B

Let M3 and C be the mass and abundance of isotopeC

Atomic mass = (M1 x A) + (M2 x B) + (M3 x C)

= (23.99x78.99%) + (24.99x10%) + ( 25.98x11.01%)

= 18.950 + 2.499 + 2.860

= 24.309

The atomic mass of magnesium is 24.309