Exploring Average Atomic Mass Concepts

The video explains the concept of average atomic mass, which is a weighted average of the mass numbers of all naturally occurring isotopes of an element. It describes how this mass is represented on the periodic table and how it can be calculated using the percent abundance of isotopes. Examples with carbon and iodine isotopes illustrate the calculation process, emphasizing that the average atomic mass is often close to the mass of the most abundant isotope.

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

• It represents the mass of the heaviest isotope.

• It is the mass of the lightest isotope.

• It is the mass of the most abundant isotope.

• It is a weighted average of all naturally occurring isotopes.

How is the average atomic mass defined?

• As the sum of the masses of all isotopes.

• As the mass of the most common isotope.

• As the mass of a single atom.

• As a weighted average of the mass numbers of all naturally occurring isotopes.

What does a weighted average take into account?

• The number of protons in the isotopes.

• The percent abundance of the isotopes.

• The number of neutrons in the isotopes.

• The chemical properties of the isotopes.

What tool is used to generate a mass spectrum?

• Spectrophotometer

• X-ray diffractometer

• Mass spectrometer

• Electron microscope

What are the two stable isotopes of carbon?

• Carbon-13 and Carbon-14

• Carbon-12 and Carbon-13

• Carbon-11 and Carbon-12

• Carbon-12 and Carbon-14

What is the percent abundance of Carbon-12 in nature?

• 99%

• 1%

• 50%

• 100%

How do you calculate the average atomic mass?

• By multiplying the mass of each isotope by its percent abundance and summing the results.

• By dividing the mass of the heaviest isotope by the number of isotopes.

• By adding the masses of all isotopes.

• By averaging the masses of the two most abundant isotopes.

What is the average atomic mass of iodine if its isotopes are I-127 (80%), I-126 (17%), and I-128 (3%)?

• 126.00 amu

• 128.00 amu

• 127.00 amu

• 126.80 amu

What is the mass of the most common isotope of iodine?

• I-128

• I-129

• I-126

• I-127

What is the final step in calculating the average atomic mass?

• Adding the percent abundances

• Dividing the sum by 100

• Subtracting the smallest mass from the largest mass

• Multiplying the sum by 100