Element X has two naturally occurring isotopes, 65X (isotopic mass 65.0457 amu, abundance 20.53%) and 67X (isotopic mass 66.9704 amu, abundance 79.47%). Calculate the atomic mass of element X.

Element X, with an atomic mass of 66.58 amu, has 2 naturally occurring isotopes, ⁶⁵X (65.0457 amu, 20.53%) and ⁶⁷X (66.9704 amu,  79.47%).

The average atomic mass (atomic mass) of an element is the sum of the masses of its isotopes, each multiplied by its natural abundance.

Element X has 2 isotopes:

We can calculate the average atomic mass of X using the following expression.

mX = m⁶⁵X × ab⁶⁵X + m⁶⁷X × ab⁶⁷X

mX = 65.0457 amu × 0.2053 + 66.9704 amu × 0.7947

mX = 66.58 amu

Element X, with an atomic mass of 66.58 amu, has 2 naturally occurring isotopes, ⁶⁵X (65.0457 amu, 20.53%) and ⁶⁷X (66.9704 amu,  79.47%).

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66.5753 amu

Explanation:

From the question given above, the following data were obtained:

Isotope A (⁶⁵X):

Mass of A = 65.0457 amu

Abundance of A = 20.53%

Isotope B (⁶⁷X):

Mass of B = 66.9704 amu

Abundance of B = 79.47%

Atomic mass of X =?

The atomic mass of X can be obtained as follow:

Atomic mass = [(mass of A × A%)/100] + [(mass of B × B%)/100]

= [(65.0457 × 20.53)/100] + [(66.9704 × 79.47)/100]

= 13.3539 + 53.2214

= 66.5753 amu

Therefore, the atomic mass of X is 66.5753 amu.

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