Atomic Mass

Front

What is atomic mass?

Back

Atomic mass is the weighted average mass of an element's isotopes, measured in atomic mass units (amu).

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How is average atomic mass calculated?

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Average atomic mass is calculated by multiplying the mass of each isotope by its relative abundance (as a decimal) and summing the results.

Front

What is an isotope?

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Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses.

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What does relative abundance mean?

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Relative abundance refers to the percentage of a particular isotope of an element compared to the total amount of all isotopes of that element.

Front

If an element has two isotopes with masses of 10 amu (20% abundance) and 12 amu (80% abundance), what is the average atomic mass?

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Average atomic mass = (10 amu * 0.20) + (12 amu * 0.80) = 11.6 amu.

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What is the average atomic mass of chlorine if it has isotopes Cl-35 and Cl-37 with a mass of 35.45 amu?

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The average atomic mass of chlorine is 35.45 amu, indicating that Cl-35 is more abundant.

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What is the significance of atomic mass in chemistry?

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Atomic mass is crucial for understanding the behavior of elements in chemical reactions and for calculating the amounts of substances involved.

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How do you determine which isotope is more abundant if given the average atomic mass?

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The isotope with a mass closer to the average atomic mass is typically the more abundant isotope.

Front

What is the average atomic mass of magnesium if its isotopes are 24 amu (79% abundance), 25 amu (10% abundance), and 26 amu (11% abundance)?

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Average atomic mass = (24 amu * 0.79) + (25 amu * 0.10) + (26 amu * 0.11) = 24.31 amu.

Front

What is the atomic mass of an element with isotopes of 10.013 amu (19.9% abundance) and 11.01 amu (80.1% abundance)?

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Average atomic mass = (10.013 amu * 0.199) + (11.01 amu * 0.801) = 10.812 amu.