Question

DUE TOMORROW: three magnesium isotopes have atomic masses and relative abundance of 23.985 amu (78.99%), 24.986 amu (10.00%), and 25.982 amu (11.01%). calculate the atomic mass of magnesium

Answer 1

Answer:

• From the formula:

${ \boxed{ \rm{ \: atomic \: mass = \frac{ \sum(isotopic \: mass \times \%abundance)}{100} }}}$

• Substitute from the information above;

${ \rm{atomic \: mass = \frac{(23.985 \times 78.99) + (24.986 \times 10.00) + (25.982 \times 11.01)}{100} }} \\ \\ { \rm{atomic \: mass = \frac{2430.49697}{100} }} \\ \\ { \boxed{ \boxed{ \rm{atomic \: mass = 24.3 \: amu}}}}$

Answer 2

Answer:

Approx. 24.3 amu.

Explanation:

The atomic mass is the weighted average of the individual isotopic masses:

(23.99 × 78.99% + 24.99 × 10.00% + 25.98 × 11.01%) · g = 24.31 · g

I have given you answer in g which here is equivalent to amu.