Question

The element copper has two stable isotopes, copper-63 with a mass of 62.93 amu and copper-65 with a mass of 64.93 amu. From the atomic weight of Cu = 63.54 one can conclude that:
- both isotopes have the same percent natural abundance
- copper-65 has the highest percent natural abundance
- most copper atoms have an atomic mass of 63.54
- copper-63 has the highest percent natural abundance

Answer 1

Answer: The Cu-63 isotope has the highest percent natural abundance

Explanation:

Average atomic mass is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

$\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i$

We are given:

Two isotopes of Copper, which are Cu-63 and Cu-65

Average atomic mass of copper = 63.54 amu

As, the average atomic mass of copper is closer to the mass of Cu-63 isotope. This means that the relative abundance of this isotope is the highest as compared to the other isotope.

Percentage abundance of Cu-63 isotope = 69.2%

Percentage abundance of Cu-65 isotope = 30.8 %

Hence, the Cu-63 isotope has the highest percent natural abundance