Relative Atomic and Isotopic Mass Concepts

This video tutorial explains the concepts of relative isotopic mass and relative atomic mass. It begins with an introduction to atomic masses and their importance in chemistry. The video then defines relative isotopic mass as the mass of an atom of an isotope compared to 1/12 the mass of carbon-12. It also covers relative atomic mass, which is the weighted mean mass of an element's atoms compared to 1/12 the mass of carbon-12. The tutorial includes examples and calculations to help viewers understand how to compute relative atomic mass using isotope data. By the end, viewers should be able to define and calculate these masses.

Why do scientists use relative masses in chemistry?

• Because it is easier to calculate with whole numbers.

• Because atoms have extremely small masses.

• Because atoms are too large to measure directly.

• Because it simplifies the periodic table.

What is the definition of relative isotopic mass?

• The mass of an atom compared to oxygen.

• The average mass of all isotopes of an element.

• The mass of an atom of an isotope compared with 1/12 the mass of carbon-12.

• The mass of an atom compared to hydrogen.

Which of the following is true about relative isotopic mass?

• It varies with temperature.

• It has units of grams per mole.

• It is always a decimal number.

• It is always a whole number.

How is relative atomic mass defined?

• The mass of an atom compared to hydrogen.

• The weighted mean mass of an atom of an element compared with 1/12 the mass of carbon-12.

• The sum of the masses of all isotopes of an element.

• The mass of an atom compared to oxygen.

Why are relative atomic masses not whole numbers?

• Because they are rounded to the nearest whole number.

• Because they are averages of isotopic masses.

• Because they are measured in grams.

• Because they include electron masses.

What is the relative atomic mass of chlorine given its isotopes?

• 36.0

• 34.5

• 37.0

• 35.5

How do you calculate the relative atomic mass of an element?

• By using the relative isotopic mass and percent abundance of each isotope.

• By averaging the masses of all isotopes.

• By adding the masses of all isotopes.

• By multiplying the mass of the most common isotope by its abundance.

What is the relative atomic mass of thallium given its isotopes?

• 202.0

• 203.5

• 205.0

• 204.4

How many isotopes does magnesium have in the given example?

• Two

• One

• Four

• Three

What is the relative atomic mass of magnesium in the example provided?

• 25.0

• 24.3

• 26.0

• 24.0