Atomic Mass Chemistry Example 3

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Example 3

medium

Chlorine has two stable isotopes:

{}^{35}\text{Cl}

(mass

34.97\,\text{amu}

, 75.77%) and

{}^{37}\text{Cl}

(mass

36.97\,\text{amu}

, 24.23%). Calculate its atomic mass.

Solution

1
$\bar{m} = (34.97 \times 0.7577) + (36.97 \times 0.2423)$ .
2
$\bar{m} = 26.50 + 8.96 = 35.45\,\text{amu}$ .

Answer

35.45\,\text{amu}

Since

{}^{35}\text{Cl}

is about three times more abundant than

{}^{37}\text{Cl}

, the atomic mass is closer to 35 than to 37.

About Atomic Mass

The weighted average mass of all naturally occurring isotopes of an element, expressed in atomic mass units (amu), where each isotope's mass is weighted by.

Learn more about Atomic Mass →

More Atomic Mass Examples

Example 1 easy

Define atomic mass and explain why the atomic mass of carbon is listed as [formula] rather than exac

Example 2 medium

Silicon has three stable isotopes: [formula] (92.23%, mass [formula]), [formula] (4.67%, mass [formu

Example 4 hard

An element has two isotopes. Isotope A has mass [formula] and isotope B has mass [formula]. The atom

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