Atomic mass is a fundamental concept in chemistry, defined as the mass of an atom measured in atomic mass units (amu). The text delves into the importance of the carbon-12 benchmark for determining atomic masses and explains how isotopic variations influence these measurements. It also covers the calculation of relative atomic mass using isotopic abundance and extends to the concepts of relative molecular mass and relative formula mass for both covalent and ionic compounds.
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Atomic mass is the mass of an atom measured in atomic mass units (amu) and is determined relative to the carbon-12 isotope
Definition of Isotope
Isotopes are variants of an element with the same number of protons but different numbers of neutrons, resulting in different atomic masses
Definition of Relative Isotopic Mass
Relative isotopic mass is the mass of a specific isotope compared to 1/12th of the mass of a carbon-12 atom
The relative atomic mass of an element is a weighted average of the masses and natural abundances of its isotopes
Relative molecular mass is the sum of the relative atomic masses of the atoms in a molecular formula
The relative molecular mass of a molecule is calculated by adding the relative atomic masses of its constituent atoms
Relative formula mass is the weighted average mass of the formula units of an ionic compound relative to 1/12th of the mass of a carbon-12 atom
The relative formula mass of an ionic compound is calculated by summing the relative atomic masses of its constituent ions
Relative mass measurements provide a standardized way to express the mass of atoms and molecules, enabling scientists to compare and communicate effectively
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One ______ is equivalent to 1/12 the mass of a ______ atom.
atomic mass unit
carbon-12
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Definition of relative atomic mass (Ar)
Dimensionless number comparing average mass of element's atoms to carbon-12 atom, divided by 12.
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Significance of carbon-12's relative atomic mass
Carbon-12's Ar is exactly 12 amu, serving as a reference point for calculating other elements' relative atomic masses.
