Isotopes and Calculating Atomic Mass

Front

What is an isotope?

Back

Isotopes are 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 average atomic mass?

Back

To calculate average atomic mass, you need the atomic mass and percent abundance of each isotope.

Front

What is the atomic mass of an isotope?

Back

The atomic mass of an isotope is the mass of a single atom of that isotope, typically measured in atomic mass units (amu).

Front

What does percent abundance mean?

Back

Percent abundance refers to the relative amount of each isotope of an element present in a naturally occurring sample.

Front

If an element has two isotopes with masses of 10.013 amu (19.9% abundance) and 11.01 amu (80.1% abundance), what is the average atomic mass?

Back

The average atomic mass is calculated as (10.013 amu * 0.199) + (11.01 amu * 0.801) = 10.812 amu.

Front

What is the significance of neutrons in isotopes?

Back

Neutrons determine the isotope of an element; different numbers of neutrons result in different isotopes of the same element.

Front

What is the atomic number of an element?

Back

The atomic number is the number of protons in the nucleus of an atom, which defines the element.

Front

How many neutrons does Li-7 have?

Back

Li-7 has 4 neutrons (7 total nucleons - 3 protons = 4 neutrons).

Front

What is the average atomic mass of an atom with 4.35% of 39.946 amu, 83.79% of 41.941 amu, 9.50% of 42.941 amu, and 2.36% of 43.939 amu?

Back

The average atomic mass is calculated as (39.946 amu * 0.0435) + (41.941 amu * 0.8379) + (42.941 amu * 0.0950) + (43.939 amu * 0.0236) = 41.97 amu.

Front

What is the relationship between isotopes and atomic mass?

Back

The atomic mass of an element is a weighted average of the masses of its isotopes, based on their relative abundances.