Patience en periodiek systeem

On February 14, 1869, Mendeleev began work on the chapter that would discuss the elements. He already believed that there was some underlying principle connecting the elements. 

He transcribed his notes onto a set of cards, one for each element containing everything he knew about that element. He arranged and rearranged the cards until he was struck by a similarity between his arrangements and those of the card game patience (solitaire), in which cards are sorted by suit and then in descending numerical order. 

Exhausted, Mendeleev fell asleep. When he awoke, he devised a grouping of the elements by common property in ascending order of atomic weight. He called his innovation the Periodic Table of the Elements.