Done by:Mohit Raj Bhurat

X B

Mendeleev's periodic table

8 February 1834 – 2 February 1907 was a Russian chemist and inventor. He formulated the Periodic Law, created a farsighted version of the periodic table of elements, and used it to correct the properties of some already discovered elements and also to predict the properties of eight elements yet to be discovered.

Dmitri Ivanovich Mendeleev

In 1863 there were 56 known elements with a new element being discovered at a rate of approximately one per year. Other scientists had previously identified periodicity of elements. John Newlands described a Law of Octaves, noting their periodicity according to relative atomic weight in 1864, publishing it in 1865. His proposal identified the potential for new elements such as germanium. The concept was criticized and his innovation was not recognized by the Society of Chemists until 1887. Another person to propose a periodic table was Lothar Meyer, who published a paper in 1864 describing 28 elements classified by their valence, but with no prediction of new elements.

Early tries..

Mendeleev becoming a teacher in 1867, Mendeleev wrote the definitive textbook of his time: Principles of Chemistry (two volumes, 1868–1870). It was written as he was preparing a textbook for his course. This is when he made his most important discovery. As he attempted to classify the elements according to their chemical properties, he noticed patterns that led him to postulate his periodic table; he claimed to have envisioned the complete arrangement of the elements in a dream."I saw in a dream a table where all elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper, only in one place did a correction later seem necessary."— Mendeleev,

His life…

Is it because he listed down the known elements ?Nah! Besides he wasn’t even the first person to do it.

SO why is he great??

Is it because he arranged elements with similar properties together ?No! that had also already been done too.

Mendeleev’s periodic table is mainly based on two facts:-i. Atomic massii. Similarity of chemical properties Mendeleev’s periodic law: “The physical and chemical properties of elements are the periodic functions of their atomic masses.”

Periodic table

If you observe the 3rd column and 5th row you will observe a dash. That dash there proves his genius. He made a very bold statement here : “We all haven't discovered this element yet, in the meantime I am going to give it a name. it is one step from aluminum so I will call it eka- aluminum” – Mendeleev.(Eka being one in Sanskrit.)

Predication of elements.

“Nobody found eka-aluminum yet so we don’t know anything about it right? Wrong. Based on where it is located I can tell you all about it.” said Mendeleev. Later he made a few conclusions about eka-aluminum. He said

Atomic weight 68 Solid metal Lustrous Heat conductivity Malleable & Ductile Melting point low Cubic cm weighs 6g.

Eka-aluminum

He basically arranged the elements according to their masses but sometimes placed a lighter element before a heavier one to satisfy that all elements in the column have similar properties.Example : In reality Nickel weighs less than cobalt but Mendeleev has placed cobalt before nickel.

Wrong order of elements

a. Position oh hydrogenHydrogen has been placed with in 1st group with the alkali metals. Hydrogen makes compound just like the alkali metals but also exist as diatomic molecule like halogens. Mendeleev could not explain about this anomaly.

b. IsotopesMendeleev could not give separate position for the isotope of a elements.

Limitations