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WHO IS MENDELEEV?
Dimitri Mendeleev was a Russian chemist, and is given credit for the periodic table. He tried to
focus on the chemical properties but he also looked at physical properties. While studying these
he kept finding similarities between the elements. He then thought that elements with similar
properties should be grouped together. He started grouping by making a card for the 63 known
elements at that time. On each card he placed the elements chemical symbol, physical
properties, and atomic mass. He then arranged the cards in increasing atomic mass and he then
noticed that elements in the same columns had the same or similar properties. He also noticed
that every element in the same column had the same number of electrons in the outer shell. He
noticed the pattern1234321 where every 7th element the pattern repeated.
In his table, which he was confident in, were blank spaces. He believed that empty spaces
were undiscovered elements. He was correct, 3 elements discovered in his lifetime fit perfectly
into the table where he thought they would. His table was good but not perfect. There were
elements out of place due to there properties. He assumed that the atomic mass was incorrectly
measured but he was incorrect. However he still had a very efficient table used to catalog
elements. His table led us to the modern periodic table that we use today.


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