History of table of Elements

        Before Dmitri Mendeleev, a French noble prominent named Antoine-Laurent de Lavoisier had made a similar type of table.  In 1789 he had grouped 33 elements into gases, metals, non-metals, and earths. Although this was a great leap in chemistry it wasn’t the best. Over the years chemists looked for more precise methods of classifications.          In 1829, Johann Wolfgang Dobereiner discovered that most of the elements could be grouped in triads. He had observed that when being arranged by atomic number the second element was the average of the first and third. This was later known as the Law of Triads.

        By 1843 a total of 10 triads were discovered. In 1858 German chemist August Kekule discovered that carbon has a tendency to bond with other elements in a ratio of one to four. This concept is called valency. Another German chemist named Julius Lothar Meyer published a table of 49 elements in 1864. The table shows that similar properties often show similar valency. The same year an English chemist named John Newlands came up with the Law of Octaves. Newland’s  papers are an attempt of classification. When elements are listed in order of increasing atomic weight, similar chemical and physical properties recurred in intervals of eight. This law was looked down by other chemists because it wasn’t significant.

        Mendeleev and Meyer both published their periodic tables in 1869. There was a lot of controversy about the first one to discover table of elements. Both constructed their tables almost identically, but Meneleev’s table was superior because of two decisions he had made. His first decision was to leave gaps in the table where elements had not yet been discovered.  This was significant because it would be easier to figure out a trend between known and unknown elements. His second decision was to sometimes ignore the order of atomic weights and switch elements adjacent  to each other. This was to better classify them into families.

        The Periodic Table of Elements has several ways of classification.  One classification is a group or family. A group is a vertical column in the periodic table. This classification is the most important because elements with similar properties show a clear trend of properties. This is important because it is easier to classify them in an orderly fashion. The groups of elements are given unsystematic names. These include the alkali metals, halogens, alkaline earth metals, and noble gases. Some groups show no similarities and are in a vertical trend. They are referred to by their group number.

        Another classification is a period.  Periods are classified in horizontal rows on the table. More commonly groups are used in classification, but in some patterns the horizontal trend is more significant. This is sometimes true in the d-block and especially in the f-block were the lanthanoids and actinoids form two horizontal series of elements.

        A third way of classification is a block. This is because of the importance of the outer most shell of an element. Different regions in the periodic table can be referred to as periodic table blocks. These are named according to were the last electron sits in the subshell.  The f-block is usually at the bottom of the periodic table and names the rarest of all the earth metals. The d-block consists of groups 3 through 12 and contains all the transition metal. The p-block consists of groups 13 through 18 and contains all the semi metals. The s-block consists of alkaline earth metals and alkaline metals as well as helium and hydrogen. Together there are four blocks.

        With the now quantum mechanical theories of electrons inside the atom, it is known that each row is congruent to the filling shell of quantum electrons. The gaps left in the periodic table are now filled. Newly discovered elements will be given systematic names because of the debate of who gets to name it. Many elements have last names in them as well as colleges or universities were the element was discovered. For example, Einsteinium was named after Albert Einstein and Helium named after the Greek god Helios. Californium was named after the University of California. As of July 2009 there are 117 known elements.