Standard periodic table, colourcoded for element types. The periodic table shows the chemical elements ordered by atomic number (number of protons in the nucleus), but arranged in rows (periods) so that elements with similar chemistry occur in the same vertical column (group). Here, blocks of elements with similar chemical properties are shown by the colours identified in the key at bottom. Each element is represented by its chemical symbol. Above each symbol is the elements atomic number, and below it is the elements name, as shown in the labelled example at lower right.
