The periodic table arranges the known elements in order of increasing atomic number, which typically coincides with increasing atomic mass. Different rows on the table are known as periods. The period number assigned to each element signifies the highest energy level an electron within the element occupies in an non-excited state.
Many of the elements of the periodic table may be categorized as either metals or non-metals. Metal elements are typically good conductors of both heat and electricity. Elements may be further categorized as alkali metals, alkaline earth metals, transition metals, metal triads, halogens, noble gases, lanthanides and actinides, depending on their properties.
The periodic table is a tabular arrangement of all known chemical elements. The table consists of four rectangular blocks, the S-, P-, D- and F-blocks. Metal elements are grouped on the left side of the table with non-metals occupying the right.
The table provides the means to derive relationships between the properties of different elements as well as to predict the properties of new and undiscovered elements. The first 94 elements on the table exist naturally, although some are only found in trace amounts. Laboratories have synthesized elements 95 to 118, and studies have shown elements 95 to 100 once existed in a natural state.