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 and compound, either of which may also be called a "substance" (which is a less specific term), and mixture - of which there are also 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 elements are included in the Periodic Table.

List of facts about Chemical Elements:

1. Elements consist of only one type of atom - which may, or may not be joined together to form molecules or large structures, so ...
2. Elements can exist either as atoms (e.g. argon) or as molecules (e.g., nitrogen)
3. 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.
4. 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 symbols of the chemical elements see pages listing these:

• 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).

Note: This is one of a series of simple pages introducing key concepts in introductory chemistry. Other pages in this section include elements, mixtures and compounds and individual pages about substances, elements, mixtures and compounds, plus pages about atoms, molecules and isotopes. If you need further information ask your chemistry tutor.