Understanding Average Atomic Mass and Weighted Averages

What are isotopes?

• Atoms with different numbers of electrons

• Atoms with the same number of neutrons but different numbers of protons

• Atoms with different numbers of protons and neutrons

• Atoms with the same number of protons but different numbers of neutrons

Why are the atomic masses on the periodic table not whole numbers?

• They represent the mass of the most common isotope

• They are rounded averages of isotopes

• They are weighted averages of naturally occurring isotopes

• They are calculated based on the number of protons

What is a weighted average?

• An average where all components are equally weighted

• An average that only considers the highest values

• An average where components have different weights

• An average calculated by adding all values and dividing by the number of values

In a weighted average, if tests are worth 50% and homework is worth 10%, how much more influence do tests have?

• Equally influential

• Twice as much

• Five times as much

• Ten times as much

How do you calculate a weighted average?

• Divide each value by its weight and sum them

• Add all values and divide by the number of values

• Multiply each value by its weight and sum them

• Multiply each value by its weight, sum them, and divide by the total weight

What is the weighted average of test scores if tests are 50%, homework is 30%, and labs are 20%?

• 80

• 83

• 85

• 90

Why is neon's average atomic mass not a whole number?

• It is calculated based on the number of electrons

• It is an average of its isotopes

• It is the mass of the most common isotope

• It is rounded to the nearest whole number

If an element's average atomic mass is closer to one isotope, what does it indicate?

• The element has no isotopes

• That isotope is less abundant

• That isotope is more abundant

• All isotopes are equally abundant

What can be inferred if chlorine's average atomic mass is 35.45?

• Both isotopes are equally abundant

• Chlorine has no isotopes

• Chlorine-35 is more abundant

• Chlorine-37 is more abundant

How can you determine the most abundant isotope of an element?

• By measuring the element's density

• By looking at the element's position on the periodic table

• By comparing the average atomic mass to the isotopes' masses

• By checking the element's atomic number