wiki Word: Atomic Mass and Mass Number

Definition: Atomic mass is the weighted average of all the natural occuring isotopes. The mass number is the number of protons and nuetrons in a single atom.

The Atomic mass and the Mass number are both the sum of the protons and nuetrons in the nucleus. The difference between them is that the mass number is the protons plus the nuetrons in a single atom but the atomic mass is the weighted average of all the isotopes of an element. For example the most common oxygen has 8 protons and 8 nuetrons so it would have a mass number of 16. The atomic mass counts those few isotopes of oxygen. 0.238% of oxygen have different numbers of nuetrons so this changes the atomic mass from 16 to approximately 15.9994. 

All of the isotopes of oxygen weighted and averaged

                     equals it's atomic mass.

 This picture shows the most common oxygen with

 8 protons and 8 nuetrons it's mass number is 16.

If you do not know the meaning and how to find the atomic mass and mass number of an atom then it would be hard to identify and classify elements. The pioneers of atomic theory, the discoverers of elements, and the firsts to classify the elements, used these often. The mass number of an element tells you the sum of the protons and nuetron and is used to show isotopes of an element. You can average the weighted mass numbers, including the isotopes to find the atomic mass. This is most commonly referred to and is on the elements periodic table square. The atomic mass and the mass number helped us understand the concepts we learned in that it showed relations between elements, it showed how big the element was and how its mass compared to other elements. These also helped us relate to eachother's elements when we lined up in a line according to our elements. When we looked at the persons beside us we saw that on one side the atomic mass was lower and on the other the atomic mass was higher. This pattern was true throughout the whole line.

 Information on atomic mass and mass number:

Wikipedia, "Atomic mass." Wikipedia. 2008. Wikimedia. 18 Mar 2008 http://en.wikipedia.org/wiki/Atomic_mass.

Picture of oxygen isotopes:

Google, "Oxygen Isotopes." Google Images. 2008. Google. 18 Mar 2008 http://images.google.com/images?gbv=2&hl=en&q=oxygen+isotopes

Picture of oxygen atom:

Google, "Oxygen Isotopes." Google Images. 2008. Google. 18 Mar 2008. http://images.google.com/images?hl=en&q=nucleus+of+oxygen+atom&btnG=Search+Images&gbv=2

The rest of the information was my own knowlege (learned from Mrs. Flynt :)