Calculating Average Atomic Mass in Atomic Structure

What are isotopes?

• Atoms of different elements with the same number of neutrons

• Atoms of the same element with varying numbers of neutrons

• Atoms of different elements with the same number of protons

• Atoms of the same element with the same number of neutrons

How are isotopes indicated?

• By their chemical properties

• By their electron configuration

• By their mass number

• By their atomic number

Which of the following is true about isotopes of carbon?

• They have different numbers of protons

• They have different chemical properties

• They have different numbers of neutrons

• They have the same mass number

Why do mass numbers of elements on the periodic table have decimals?

• Because they are exact masses of the most common isotope

• Because they are weighted averages of all the isotopes

• Because they include the mass of electrons

• Because they are rounded to the nearest whole number

What is the first step in Method 1 for calculating average atomic mass?

• Multiply the percentage of each isotope by its mass number

• Add the masses of all isotopes

• Convert percentages to decimals

• Divide the sum by the number of isotopes

In Method 1, what do you do after multiplying the percentage of each isotope by its mass number?

• Subtract the smallest mass number

• Add the results together

• Divide by the number of isotopes

• Convert the result to a decimal

What is the first step in Method 2 for calculating average atomic mass?

• Add the masses of all isotopes

• Divide the sum by the number of isotopes

• Convert percentages to decimals

• Multiply the mass number by 100

In Method 2, what do you do after converting percentages to decimals?

• Add the results together

• Multiply the decimal by its associated mass

• Divide by the number of isotopes

• Subtract the smallest mass number

What is the average atomic mass of chlorine if chlorine-35 has a natural abundance of 75.5% and chlorine-37 has a natural abundance of 24.5%?

• 36.49 u

• 37.49 u

• 35.49 u

• 34.49 u

What is the average atomic mass of silicon if silicon-28 is 92.23%, silicon-29 is 4.68%, and silicon-30 is 3.09%?

• 27.1 u

• 28.1 u

• 29.1 u

• 30.1 u