Bromine-79 (50.7% abundance) has an atomic mass of 78.918 amu, whereas bromine-81 (49.3% abundance) has an atomic mass of 80.916 amu. From these data, calculate the average atomic mass of bromine that you would expect to see in the periodic table.

검증된 단계별 안내

Step 1: Understand the concept of average atomic mass. The average atomic mass of an element is calculated as the weighted average of the atomic masses of its isotopes, based on their relative abundances.

Step 2: Write the formula for calculating the average atomic mass:

Average atomic mass = (Fractional abundance of isotope 1 \times Mass of isotope 1) + (Fractional abundance of isotope 2 \times Mass of isotope 2)

Step 3: Convert the percentage abundances of bromine-79 and bromine-81 into fractional abundances by dividing each percentage by 100. For bromine-79, the fractional abundance is

50.7 / 100

, and for bromine-81, the fractional abundance is

49.3 / 100

Step 4: Substitute the fractional abundances and atomic masses of bromine-79 and bromine-81 into the formula. This gives:

(0.507 \times 78.918) + (0.493 \times 80.916)

Step 5: Perform the multiplication and addition to calculate the average atomic mass. This result will represent the average atomic mass of bromine as it appears in the periodic table.

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주요 개념

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Atomic Mass

Atomic mass is the weighted average mass of an element's isotopes, measured in atomic mass units (amu). It reflects both the mass of each isotope and its relative abundance in nature. For bromine, the atomic masses of its isotopes, bromine-79 and bromine-81, are crucial for calculating the average atomic mass.

Isotopes

Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses. In the case of bromine, the two isotopes, bromine-79 and bromine-81, have different atomic masses and relative abundances, which must be considered when calculating the average atomic mass.

Weighted Average Calculation

A weighted average calculation involves multiplying each value by its corresponding weight (or abundance) and then summing these products before dividing by the total of the weights. For bromine, this means calculating the contributions of each isotope's mass based on its abundance to find the average atomic mass that appears on the periodic table.