The 33 elements, and he categorised them
The Periodic Table:From early 400 BCE all the way to present day, the periodic table and its respective elements have been the subject of much scientific research. The table forms the basis of all modern chemistry, only available now due to the hundreds of years of previous research.One of the first instances which began the evolution of chemistry, and eventually the table, was when, in 440 BCE, two Greek scientists, Democritus and Leucippus theorised about the idea of an atom. The theory that there was a particle that made up all matter. Shortly after this theory, Aristotle, in 330 BCE, introduced the four elements theory (fire, water, earth and air). After quite a period of time in which practices such as alchemy (the practice in which people believed they were able to turn base metals into gold, find the elixir of life etc.) emerge.
Then, in 1661 CE, the book ‘The Sceptical Chymist’ is published by Robert Boyle. It contained rudimentary ideas of atoms and molecules; this is thought to mark the beginning of modern chemistry. In 1754 CE Joseph Black is able to isolate carbon dioxide.
This led to the further discovery of respiratory gases. In 1766 CE, Henry Cavendish isolates the element hydrogen, realising it is a gas that has a high reactivity to fire.The first list of elements is finally constructed by Antione Lavoisier in 1778 CE.
It contained 33 elements, and he categorised them into metals and nonmetals. One of the first scientists that constructed the elements into a table that resembles the one used today was Jakob Berzelius, in 1828, using the atomic symbols and atomic weights. Three discoveries were made in 1864 CE; John Newlands arranged all known elements in accordance to their atomic weight; observing some similar characteristics between them. Meanwhile, Lothar Meyer created an early periodic table, which consisted of 28 elements, sorted by valence (electrons on the outside shell). Also in the same year, Dmitri Mendeleev created a table containing 66 elements, arranged periodically and by atomic weights.
Dmitri Mendeleev was born in Tobolsk, Russia, on February the 8th, 1834 and died on February the 2nd, 1907 in St. Petersburg, Russia. Mendeleev’s father died in 1847, causing his mother to become the manager of a glass factory to support the family.
When the glass factory burnt down in 1848, the family decided to move to St. Petersburg. For his education he attended the Main Pedagogical, before studying abroad. He later returned to St. Petersburg, where he received his Masters Degree.
While he was teaching chemistry (inorganic), he could not find a textbook or reference that met his educational needs. He began to write his own textbook to explain the theory. As he wrote the chapter on halogen elements, he began to compare them to alkali metals. He established the because similarities existed between multiple groups, the atomic numbers could not only be used to establish an order within the elements own group, but also order the elements as a whole.
Thus, he began to create a ‘table of elements’. In doing this, he began to discover Periodic Law. Because his table was arranged ‘periodically’, not only was it able to show the placement of known elements, it was also able to predict the yet undiscovered elements as well.Shortly after, in 1894 CE, William Ramsay discovers the concept of Noble Gases; followed in 1913 CE by Henry Mosley when he sets the atomic number for each elements, thus modifying the ‘Periodic Law’. A small period passes before Glenn Seaborg, in 1945 CE, identifies elements with atomic numbers higher than 92. This precedes all the way to 2006 onwards, where there are currently 118 elements on the modern Periodic Table.