Answer the following question given this paragraph: 

An element is the simplest form of matter that has a unique set of properties. Examples of well-known elements include oxygen, iron, and gold (see the figure below). Elements cannot be broken down into a simpler substance. Likewise, one element cannot be chemically converted into a different element.


Q: What is the term for the simplest form of matter that has a unique set of properties?


A:
an element