What is an Element (in terms of Chemistry)?
Matter can be classified in various ways according to its structure, behaviours and physical and chemical properties.
The main classifications of matter include the categories:
- element which may also be called a 'substance' (a less precise word)
- compound which may also be called a 'substance' (a less precise word), and
- mixture, of which there are many sub-categories.
Definition of a Chemical Element:
An element is a chemical substance that cannot be broken-down into any simpler substances by chemical reactions. It consists of only one type of atom, though the atoms of an element may, or may not, join together to form molecules (that depends on the particular element and so the structure of its atoms).
All the elements are included in the Periodic Table.
List of facts about Chemical Elements:
- Elements consist of only one type of atom - which may, or may not be joined together to form molecules or large structures, so ...
- Elements can exist either as atoms (e.g. argon) or as molecules (e.g., nitrogen)
- Elements cannot be broken down into a simpler type of matter by either physical or chemical techniques - though some larger elements break-down spontaneously due to being radioactive.
- Elements are listed in the periodic table.
Symbols of Chemical Elements:
Every chemical element has its own symbol.
Examples of chemical symbols are N (for the element nitrogen), He (for the element helium) and Pb (for the element lead).
For more about the symbols of the chemical elements see pages listing them in the following ways:
- in order of their atomic number, or
- alphabetically in order their chemical symbol or
- alphabetically in order the name of the element in English.
Many elements are found in nature and so may be called "naturally occurring elements". Other elements have not been found in nature but can be produced in the laboratory. A few more chemical elements are thought to exist but are very rare and even if produced would only exist for a very short time because they are radioactive and would quickly decompose into other elements whose atoms are smaller.
Do elements consist of atoms or molecules ?
Some elements exist in the form of atoms e.g. the noble bases neon (Ne), argon (Ar), krypton (Kr), xeon (Xe) and radon (Rn).
Other elements exist in the form of molecules. For example many common gases exist as diatomic molecules e.g. oxygen (O2), hydrogen (H2), and nitrogen (N2).
In the diagram shown above:
Atoms are represented by single spheres.
Spheres of the same size and colour represent atoms of the same element.
Molecules are represented by two or more spheres joined together.
Hence molecules of elements are represented by two or more spheres of the same size and colour joined together.