Why Aren't All Atomic Masses Whole Numbers?

The video explains that atomic masses are not always whole numbers due to isotopes, which are atoms of the same element with different numbers of neutrons. Using chlorine as an example, the video shows how the relative abundance of isotopes affects the calculation of relative atomic mass. A formula is provided to calculate this weighted mean mass. Another example with bromine is given to reinforce the concept. The video concludes by emphasizing that the relative atomic mass is a weighted mean of isotopes, explaining why these values are not whole numbers.

What are isotopes?

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

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

• Atoms with different numbers of electrons

• Atoms with different numbers of protons and neutrons

Which isotopes of chlorine are most common in nature?

• Chlorine 34 and Chlorine 36

• Chlorine 35 and Chlorine 37

• Chlorine 36 and Chlorine 38

• Chlorine 33 and Chlorine 35

How is the relative atomic mass of an element calculated?

• By averaging the atomic masses of all isotopes

• By adding the atomic numbers of all isotopes

• By considering the most abundant isotope only

• By using the weighted mean of isotopes based on their abundance

What is the relative atomic mass of bromine if it contains 50% bromine 79 and 50% bromine 81?

• 79

• 80

• 82

• 81

Why are most relative atomic masses not whole numbers?

• Because of the presence of isotopes with different masses

• Due to errors in measurement

• Because elements can lose electrons

• Due to the presence of radioactive isotopes