Indium (In) has two naturally occurring isotopes: In-113 and...

Indium (In) has two naturally occurring isotopes: In-113 and In-115. In-113 has a $4.30 \%$ abundance and a mass of $112.9 \mathrm{amu}$, and In-115 has a $95.70 \%$ abundance and a mass of $114.9 \mathrm{amu}$. Calculate the atomic mass for indium using the weighted average mass method. (4.5)

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Key Concepts

Atomic Mass

Atomic mass is the average mass of an element's atoms as they are found in nature, taking into account the masses and the relative abundances of the different isotopes of the element. It is not the exact mass of a single atom, but rather a calculated value that reflects the weighted contributions of each isotope.

Isotopes

Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons, leading to different masses. They are essential in understanding atomic mass because the element's average atomic mass is derived from the masses of its isotopes.

Weighted Average

The weighted average method involves multiplying each isotope's mass by its relative abundance and then summing these values. This calculation gives a more accurate representation of an element's atomic mass as it accounts for the varying contributions of each isotope.

Abundance

Abundance refers to the fraction or percentage of each isotope present in a naturally occurring sample of the element. These values are used as weights in the weighted average calculation, determining the influence each isotope's mass has on the overall atomic mass.

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