So how has the periodic table been put together? Mrs Roberts: Well, the modern periodic table shows us all of the elements arranged in rows, which are called periods. It has changed a lot over the ...

In 1843, Leopold Gmelin worked with the Dobereiner’s system and developed a table of 55 elements that contained many of the similar relationships later found in the modern periodic table. Then in 1857 ...

Thus, in the modern periodic table, the elements are arranged according to their atomic number - not their relative atomic mass. "We now know the 'how it works, why it works', and this is to do ...