Only two isotopes of copper occur naturally: 63 Cu (atomic...

Only two isotopes of copper occur naturally: 63 Cu (atomic mass $=62.9296$ amu; abundance 69.17$\%$ and 65 (atomic mass $=64.9278$ amu; abundance 30.83$\%$ ). Calculate the atomic weight (average atomic mass) of copper.

Key Concepts

Isotopes

Isotopes are variants of a chemical element that have the same number of protons but differ in the number of neutrons. This difference in neutron count results in different atomic masses while the chemical properties remain nearly identical. The concept is essential for understanding variations in atomic mass and the naturally occurring composition of elements.

Isotopic Abundance

Isotopic abundance refers to the percentage of each isotope present in a natural sample of an element. When calculating properties like the atomic weight, the abundance of each isotope is used to determine how much each contributes to the overall average. This concept is crucial for understanding measurements that are based on natural samples rather than pure isotopic forms.

Atomic Weight (Average Atomic Mass)

Atomic weight, also known as average atomic mass, is the weighted average of the masses of all isotopes of an element, taking into account their relative abundances. It reflects the average mass of an atom of an element as found in nature and is used in chemical calculations and equations.

Weighted Average Calculation

The weighted average calculation involves multiplying the mass of each isotope by its relative abundance and then summing these products. This process gives a more accurate representation of an element's atomic weight by considering the contribution of each isotope, rather than simply taking an arithmetic mean of the mass numbers.

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