Average Atomic Mass

Front

What is average atomic mass?

Back

The weighted average of the masses of an element's isotopes, taking into account their relative abundances.

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 masses.

Front

How do you calculate average atomic mass?

Back

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

Front

What is relative abundance?

Back

The percentage of a particular isotope compared to the total amount of all isotopes of that element.

Front

If an isotope has a mass of 10 amu and is 50% abundant, what is its contribution to the average atomic mass?

Back

5 amu (10 amu * 0.50).

Front

What is the average atomic mass of an element with two isotopes: 10 amu (20% abundance) and 12 amu (80% abundance)?

Back

11.6 amu (10 amu * 0.20 + 12 amu * 0.80).

Front

What does amu stand for?

Back

Atomic mass unit, a standard unit of mass that quantifies mass on an atomic or molecular scale.

Front

Why can't you determine the average atomic mass with only the masses of isotopes?

Back

You also need to know the relative abundances of each isotope.

Front

What is the average atomic mass of an element with isotopes of 5 amu (30% abundance) and 7 amu (70% abundance)?

Back

6.4 amu (5 amu * 0.30 + 7 amu * 0.70).

Front

What is the significance of average atomic mass in chemistry?

Back

It helps predict how elements will react and combine with others based on their isotopic composition.