# An element has three naturally occurring isotopes with the following masses and abundances. How do you calculate the atomic mass of this element? What is the identity of the element?

##
Isotopic Mass (amu) Fractional Abundance

38.964 0.9326

39.964 #1.000 xx 10^(-4)#

40.962 0.0673

Isotopic Mass (amu) Fractional Abundance

38.964 0.9326

39.964

40.962 0.0673

##### 1 Answer

The element is potassium, and its atomic mass is 39.10 u.

#### Explanation:

The atomic mass is the weighted average of the atomic masses of each isotope.

In a **weighted average**, we multiply each value by a number representing its relative importance.

In this problem, the fractional abundance represents the relative importance of each isotope.

Here's how to do the calculation:

The atomic mass of the element is **39.10 u**.

The element is **potassium**.