The periodic table of chemical elements, often called the periodic table, organizes all discovered chemical elements in rows (called periods) and columns (called groups) according to increasing atomic ...

2nd Period: Lithium to neon—Electrons go into the second level. After the second level has 8 electrons, the next electron goes into the third level. 3rd Period: Sodium to argon—Electrons go into the ...

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 ...