What is Atomic Mass defined as?

What is Atomic Mass defined as?

• A. Mass number of the most abundant isotope
• B. Average mass of atoms of an element
• C. Mass of a single atom
• D. Mass per mole of a substance

Answer: (B)

Atomic mass is the weighted average mass of the atoms of an element, taking into account the different isotopes and their natural abundances, and is expressed in atomic mass units. This is why the correct choice is the average mass of atoms of an element—the mass you get when you average over all the isotopes that exist and how common each one is. The mass of a single atom would correspond to a specific isotope, not the element as it occurs in nature. The mass per mole describes molar mass, which is related but a different concept (it's the mass of a quantity of atoms measured in grams per mole). The mass number of the most abundant isotope ignores other isotopes and their contributions, so it doesn’t represent the element’s overall atomic mass.

Atomic mass is the weighted average mass of the atoms of an element, taking into account the different isotopes and their natural abundances, and is expressed in atomic mass units. This is why the correct choice is the average mass of atoms of an element—the mass you get when you average over all the isotopes that exist and how common each one is. The mass of a single atom would correspond to a specific isotope, not the element as it occurs in nature. The mass per mole describes molar mass, which is related but a different concept (it's the mass of a quantity of atoms measured in grams per mole). The mass number of the most abundant isotope ignores other isotopes and their contributions, so it doesn’t represent the element’s overall atomic mass.