Question

An element has two naturally occurring isotopes. one has an abundance of 37.40% and an isotopic mass of 184.953 amu, and the other has an abundance of 62.60% and a mass of 186.956 amu. what is the atomic weight of the element?

Answer 1

The atomic weight of an element depends on masses of its isotopes and their abundance.

The mass and abundance of first isotope is 184.953 amu and 37.40% respectively and that of second isotope is 186.956 amu and 62.60% respectively.

The atomic weight of element can be calculated using the following formula:

Atomic weight=% isotope-1× mass (isotope-1)+% isotope-2× mass (isotope-2)

Putting the values,

Or,  

Therefore, atomic weight of the element is 186.207 amu.

Answer 2

The atomic weight of an element depends on masses of its isotopes and their abundance.

The mass and abundance of first isotope is 184.953 amu and 37.40% respectively and that of second isotope is 186.956 amu and 62.60% respectively.

The atomic weight of element can be calculated using the following formula:

Atomic weight=% isotope-1× mass (isotope-1)+% isotope-2× mass (isotope-2)

Putting the values,

$Atomic weight=(\frac{37.40}{100})(184.953 amu)+(\frac{62.60}{100})(186.956 amu)$

Or, $Atomic weight =(69.172+117.034)amu=186.207 amu$

Therefore, atomic weight of the element is 186.207 amu.