Understanding Isotopes and Percent Abundance

What is an isotope?

• A different element with the same atomic number

• A version of an element with a different number of neutrons

• A molecule with a different number of electrons

• A compound with a different atomic mass

Which of the following is true about isotopes of the same element?

• They have the same number of neutrons

• They have different atomic numbers

• They have different chemical symbols

• They have the same number of protons

How do you convert a percentage to a decimal for calculations?

• Multiply by 10

• Divide by 10

• Multiply by 100

• Divide by 100

What is the first step in calculating the average atomic mass of an element with multiple isotopes?

• Subtract the smallest mass from the largest

• Multiply the mass of each isotope by its percentage

• Convert percentage abundances to decimals

• Add the masses of all isotopes

Why do we round the final average atomic mass to four significant figures in the example?

• Because the periodic table uses four significant figures

• To match the number of significant figures in the given data

• To simplify the calculation

• Because isotopes always have four significant figures

In the copper example, what does 'X' represent in the percent abundance formula?

• The mass of the first isotope

• The number of neutrons in the first isotope

• The percentage of the first isotope

• The total atomic mass

How do you find the percentage of the second isotope if you know the percentage of the first?

• Multiply the percentage of the first isotope by 2

• Add the percentage of the first isotope to 100

• Divide the percentage of the first isotope by 2

• Subtract the percentage of the first isotope from 100

What is the final step in determining the percent composition of isotopes?

• Convert the decimal to a percentage by multiplying by 100

• Add the percentages of all isotopes

• Subtract the smaller percentage from the larger one

• Divide the total mass by the number of isotopes

What is the average atomic mass of copper given in the example?

• 65.000 amu

• 63.546 amu

• 64.9278 amu

• 62.9296 amu

What should students do if they feel unprepared for their exam?

• Ignore the exam and hope for the best

• Rely on classmates for answers

• Review the video and practice problems

• Only study the night before