The periodic table was first developed in 1789 by Antoine Lavoisier, who listed 33 known chemical elements, although Dmitri Mendeleev is generally acknowledged as the first to arrange the periodic table in the manner now used. He also used the properties of the groups to correctly deduce gaps where elements, which had not been discovered would belong. The table has been continually modified as new elements have been discovered, the last of which being ununquadium (114) and ununhexium (116), which were accepted in June 2011. The table now consists of 118 chemical elements, placed specifically in order to show trends. The organization of the table allows one to predict the properties of an element given its location in the table.
The known elements are organised into groups based on properties, and ordered using atomic numbers. Groups are labelled from 1-8 starting on the left with group 1 and ending on the right with group 8 (the transition metals are not traditionally assigned groups due to their varying properties). Group 1 contains the alkaline metals and hydrogen, Group 2 the alkali earth metals and group 8 holds the noble gases.
Information included in a periodic table includes: atomic number, weight, name and symbol, whilst the charge of the ions of the elements in groups 1-8 can be determined.
It should be noted that not all periodic tables will contain the information listed before. Some periodic tables may only give the symbol, and others may give more information, such as the states of the element is when at certain temperatures.