The periodic table is a chart designed to classify known elements. The periodic table is a tool of chemistry which contributes to the understanding of matter. Phoenix Learning Group explains the periodic table as a map. The elements can be placed on the periodic table as metals, metalloids, and non-metals. Most of the elements on the table are metals. There are a total of 118 elements listed on the periodic table. The elements are organized by atomic number . The atomic number is the total number of protons in the element. The group represents elements with similar valence electron counts. The columns of the periodic table are the groups. The periods on the chart show elements with the same number of electron shells. The periods are placed in the rows of the chart. To determine the number of neutrons the atomic number must be subtracted from the mass number. Understanding the attributes of elements has enabled chemical engineering. These are the elements known on Earth. There remains a possibility more could exist in the universe. The two mots abundant elements are hydrogen and helium.