Relative atomic mass

Relative Atomic Mass

The relative atomic mass (also known as atomic weight) of an element is a measure of the mass of its atoms relative to the mass of a carbon-12 atom, which is defined as exactly 12 atomic mass units (amu). This value is a dimensionless quantity, as it is a ratio of two masses.

Periodic Table by Atomic Weight

The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties. Elements are presented in order of increasing atomic number. The standard form of the periodic table includes the elements' relative atomic masses.

Calculation of Relative Atomic Mass

The relative atomic mass of an element is calculated as the weighted average of the atomic masses of its naturally occurring isotopes. The formula used is:

\[ \text{Relative Atomic Mass} = \sum ( \text{isotope abundance} \times \text{isotope mass} ) \]

For example, the relative atomic mass of chlorine is calculated using the masses and abundances of its two stable isotopes, chlorine-35 and chlorine-37.

Importance in Chemistry

Relative atomic mass is crucial in stoichiometry, which involves the calculation of reactants and products in chemical reactions. It is also essential in determining the molar mass of compounds, which is used in various chemical calculations.

Related Pages

• Atomic number
• Isotope
• Molar mass
• Periodic table
• Chemical element
• Stoichiometry

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