Isotopesįor us to completely understand atomic mass we have to first understand isotopes. We find that Fe has about 30 neutrons in its nucleus. Iron has 26 protons and if we use the formula

Look at this example of the element Iron (Fe). If you know how many neutrons an unknown element has (which you normally would from the periodic table) than you can always calculate the number of protons, and since protons never differ in an element you can figure out the identity of the unknown element. This is what is used to calculate an atoms mass number. The number of protons, Z, and the number neutrons make up the mass number, denoted as the letter A. This is usually denoted by the letter “Z.” An atom is usually made up of protons neutrons and electrons, but since electrons are generally so small only protons and neutrons account for the mass of an element. In chemistry the amount of protons in an atom is referred to as its atomic number. all atoms with one proton are hydrogen atoms. The protons within the nucleus of an atom are what make an element an element.

Isotope Abundance and Average Atomic MassĪtoms of any element contain a certain amount of protons.

What makes up an atom, and how to determine atomic masses. In this article you will learn about the different things that contribute to atomic mass.

Formula for atomic mass number