ELEMENTS An ELEMENT is the simplest form of matter which can not be changed further by chemical or physical methods. An ATOM is the simplest form of an element.

The simplest form of some elements is a MOLECULE. When an element consists of two identical atoms it is called a diatomic molecule. For example oxygen in air consists of molecules containing two atoms of oxygen, (written as O2).

All natural matter is composed of atoms containing some 92 elements. Another 10-12 elements are man-made. A number of elements exist in a pure form in nature such as oxygen and nitrogen (in air), gold, silver, carbon (graphite and diamonds), and sulfur. A few very familar elements include: iron in steel, copper in pipes in your house or the copper coating on pennies, and aluminum popcans.

The elements are arranged into a table called the PERIODIC TABLE OF THE ELEMENTS. There are many web based versions of the table, with one of the best called WebElements.

SYMBOL	COMMON ELEMENTS	BRIEF DESCRIPTION
H	Hydrogen	Lightest by weight, a gas not found in air, very flammable
C	Carbon	"Lead" in pencils - graphite, diamonds
N	Nitrogen	Gas present in air, used as a liquid in demonstrations
O	Oxygen	Gas present in air, reacts with most other elements
Na	Sodium	A soft silvery metal, very reactive in water
Mg	Magnesium	Grey metal, used in alloys
Al	Aluminum	Grey metal used in beverage cans
S	Sulfur	A yellow solid, reacts with many elements
Cl	Chlorine	Used in tap and pool water to kill bacteria, a pale yellow gas
Cu	Copper	Orange/brown metal used in pipes
Zn	Zinc	Grey metal used to coat iron as in galvanized iron
I	Iodine	Purple solid, gives blue color with starch