3.3 Atomic Mass

Front

What is atomic mass?

Back

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

Front

What is an isotope?

Back

Atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses.

Front

How do you calculate the average atomic mass of an element with multiple isotopes?

Back

Multiply the mass of each isotope by its relative abundance (as a decimal), then sum these values.

Front

What is the relative abundance of an isotope?

Back

The percentage of a specific isotope present in a naturally occurring sample of an 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?

Back

11.6 amu.

Front

What is the significance of the atomic mass listed on the periodic table?

Back

It represents the average atomic mass of all isotopes of an element, weighted by their natural abundances.

Front

Which isotope of chlorine is more abundant if the atomic mass is 35.45 amu?

Back

Cl-35 is more abundant.

Front

What is the atomic mass of Uranium?

Back

238.03 amu.

Front

How do you determine which element corresponds to a given average atomic mass?

Back

Compare the calculated average atomic mass with the atomic masses listed on the periodic table.

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)?

Back

24.31 amu.