Question: how did people invent the periodic table?

Richard Unwin answered on 12 Nov 2015:

There were a few attempts to develop a ‘periodic table’. that is a way of ordering the elements, before the one we know today. It is said that the Russian chemist who developed the modern periodic table, Dimitri Mendeleev, played with cards which had all of the elements and some facts about their properties written on them when he was on long train journeys. Either way, he arranged them, in order of atomic mass, such that the elements in the same column shared certain properties, in a layout roughly similar to that we know today. In Mendeleev’s day, there were lots of gaps in the table, but since then we have discovered elements that ‘fit’ into those gaps which have properties that Mendeleev (and others) predicted from the table, which is really impressive!