Atomic weight – Definition & Meaning

Atomic weight is an essential concept in the field of chemistry. It is a measure of the average mass of atoms of an element, taking into account the relative abundance of isotopes. In this article, we will explore the definition and meaning of atomic weight, its origin, and its significance in different contexts.


Atomic weight is defined as the average mass of an atom of an element, expressed in atomic mass units (amu). It takes into account the relative abundance of all the naturally occurring isotopes of the element. The atomic weight of an element is a constant value, and it is used to calculate the molecular weight of compounds.


The concept of atomic weight dates back to the 19th century when chemists began to study the properties of elements and their compounds. The first systematic attempt to determine atomic weights was made by John Dalton in the early 1800s. He proposed a system of atomic weights based on the relative weights of atoms of different elements.

Meaning in different dictionaries

According to the Merriam-Webster dictionary, atomic weight is defined as “the average weight of an atom of an element, measured in atomic mass units.” The Oxford English Dictionary defines it as “the relative weight of an atom of a particular element compared with the weight of an atom of carbon-12.”


Atomic weight is closely associated with the concept of isotopes. Isotopes are atoms of the same element that have different numbers of neutrons in their nuclei. The relative abundance of isotopes affects the atomic weight of an element.


Some synonyms of atomic weight include atomic mass, relative atomic mass, and atomic number.


There are no antonyms of atomic weight.

The same root words

Some related terms that share the same root words as atomic weight include atomic mass unit, atomic number, and isotopes.

Example Sentences

  1. The atomic weight of carbon is 12.01 amu.
  2. The atomic weight of hydrogen is 1.008 amu.
  3. The atomic weight of an element is calculated by taking the weighted average of the masses of all its isotopes.
  4. The atomic weight of an element is an important factor in determining its chemical properties.
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