Write 10 lines about Mendeleev.
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Answer:
The crucial credit for classifying elements goes to Dmitri Ivanovich Mendeléev, a Russian chemist.
He was a significant donor in the premature development of a Periodic Table of elements.
When he started his work, 63 elements were known.
He studied the relationship between
the atomic weights of the elements and their physical and chemical properties.
In chemical properties, he paid attention on the compounds formed by elements with oxygen and hydrogen.
Since hydrogen and oxygen are very reactive and formed compounds with most elements, he chose them.
63 cards was taken by him and on each card, the properties of one element was written down by him.
When he grouped together the elements with similar properties, he found that most of the elements were arranged in the order of their increasing atomic weights.
He arranged the elements in the form of a table where elements having similar properties were placed one below the other.
He also noticed that the elements with similar properties take place after a fixed interval.
On this basis, he prepared a Periodic Law, which states that 'the properties of elements are the periodic function of their atomic masses'.
In his periodic table, the vertical columns were called groups and the horizontal rows were called periods.
In 1872, his periodic table was first published in a German journal.
At the top of each column, the general formula for oxides and hydrides were given.
There, the letter 'R' was used to show any of the elements in the group.
He made decision of the location of an element in a group based on the chemical compounds formed by it.
The formula of the compounds was used by him to determine their valency.
He gave number to a group that showed its valency in relation to oxygen.