Elements are pure chemical substances of one type of atom. Elements come together to produce more complex compounds, but the periodic table only contains information about each type of pure chemical atom.
Elements are placed on a periodic table according to their atomic structure. On the periodic table, elements are identified by their chemical symbol. Carbon's chemical symbol is C. Most of the symbols for elements are based on abbreviations of their english name.
Each vertical column of elements on the periodic table is called a group. Groups of elements on the periodic table are determined by the number of valence electrons atoms of the element have in their outer most energy level. As groups move from left to right on the periodic table, the number of valence electrons an atom contains increases.
The horizontal rows on the periodic table are known as periods. Each period on the periodic table displays elements in increasing atomic mass and atomic number from left to right. Periods on the periodic table can be used to indicate the number of electron shells (orbitals) an element has.