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# Elements

A chemical element is a substance made up of only one type of atom. This includes isotopes of that particular atom, which only differ in the number of neutrons present.

Elements are the simplest pure substances in nature and cannot be broken down further into simpler pure substances.

An element can occur in nature as a single atom or as a molecule containing more than one atom.

Neon gas exists as single atoms ($\ce{Ne}$) while hydrogen gas exists as a molecule consisting of two hydrogen atoms ($\ce{H2}$).

As of 2011, there are 118 known chemical elements. Many of these elements do not exist naturally but have been created in a laboratory.

All matter is made of these elements or various combinations of these elements. The following table shows images of some elements.

Neon gas: $\ce{Ne}$
Bromine liquid: $\ce{Br}$
Iron: $\ce{Fe}$
Gold: $\ce{Au}$