Matter has mass and takes up space. Atoms are a pure substance of matter and cannot be broken down into smaller chemical substances.

“The word atom is derived from the Greek word atom which means indivisible. The Greeks concluded that matter could be broken down into particles to small to be seen. These particles were called atoms”

Atoms are made up of three types of Particles: Protons, Neutrons, and Electrons. Protons and neutrons are in charge of most of the atomic mass. The mass of an electron is very small (9.108 X 10-28 grams). Both the protons and neutrons are contained in the nucleus. Protons have a positive (+) charge, neutrons have no charge, they are neutral. Electrons orbit in rings around the nucleus. They have a negative charge (-).

The atomic number of an atom is based on the amount of protons it contains, but neutron number may vary, so mass number (protons + neutrons) may vary.

The same element can contain different numbers of neutrons; this particular form of an element is called an Isotope. Isotopes have the same chemical properties, but the physical properties of some isotopes may be different. Certain Isotopes have a property that makes them Radioactive or they radiate energy as they decay into a more stable form, perhaps another element half-life: how long it takes for half of the atoms in an element to decay into a stable form. Another example is oxygen, with atomic number of 8 can have 8, 9, or 10 neutrons.

So, What is an element?

All matter is made up of elements that cannot be broken apart into smaller elements. There are 92 elements that occur in the natural world. The elements hydrogen, carbon, nitrogen and oxygen are the elements that make up most living things. A few other elements found in living thing are: magnesium, calcium, phosphorus, sodium, potassium.

Some time before the 18th century, many elements had already been discovered. The scientist Dmitri Mendeleev, theorized an arrangement of know elements based on their atomic mass. That arrangement today is known as the Periodic Table of Elements.

The Octet Rule

Every Atom pretty much has an attraction to be exactly like the nearest noble gas in atoms. In noble gases the outer electron shell is complete. This means that it will give away or steal electrons from other atoms to do so.