What are elements?

All matter is made up of elements which are fundamental substances which cannot be broken down by chemical means. There are 92 elements that occur naturally. The elements hydrogen, carbon, nitrogen and oxygen are the elements that make up most living organisms. Some other elements found in living organisms are: magnesium, calcium, phosphorus, sodium, potassium.

By the late 1800's many elements had already been discovered. The scientist Dmitri Mendeleev, a Russian chemist, proposed an arrangement of know elements based on their atomic mass.

The modern arrangement of the elements is known as the Periodic Table of Elements and is arranged according to the atomic number of elements.

Note that an element:

• consists of only one kind of atom,
• cannot be broken down into a simpler type of matter by either physical or chemical means, and
• can exist as either atoms (e.g. argon) or molecules (e.g., nitrogen).

The periodic table of the chemical elements is a tabular display of the known chemical elements. The elements are arranged by electron structure so that many chemical properties vary regularly across the table. Each element is listed by its atomic number and chemical symbol.