<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties . This adopted ordering shows periodic trends, such as elements with similar behaviour in the same column . It also shows four rectangular blocks with some approximately similar chemical properties . Generally, within one row (period) the elements are metals on the left, and non-metals on the right . Table rows are called periods and columns are called groups . Six groups have accepted names as well as assigned numbers: for example, group 17 elements are halogens; and group 18 are noble gases . </P> <P> Importantly, the periodic table can be used to derive relationships between element properties, but also predicting behaviours or chemical properties of undiscovered or newly synthesized elements . The modern periodic table provides a useful framework for analyzing chemical reactions, and continues to be widely adopted in chemistry and other sciences . </P>

What do the columns and rows on the periodic table represent