Mrs Roberts: Well, elements that have similar properties to each other are put into vertical columns called groups. Now, the table is called the periodic table because the elements with similar ...

The records show that Mendeleev discovered the periodic system on 17 February 1869. In fact, he was ill at the time so his colleague Nikolai Menschutkin made the announcement on his behalf – on 6 ...

The Periodic Table of Elements. Each entry contains the atomic number, chemical symbol, and atomic mass to two decimal places on elements where data is available. Undefined cells contain a space. Row ...