• Question: why is there a periodic table?

    Asked by anon-353983 on 20 Mar 2023.
    • Photo: Edward Guy

      Edward Guy answered on 20 Mar 2023: last edited 20 Mar 2023 3:42 pm

      The periodic table was set out to allow chemical elements with similar properties to be grouped together. Back at the time, atomic mass of elements was known, so all the elements could be placed in order of their increasing mass. So, for example, all the inert (noble) gases could be put in one column and all the metals that react with water to form sodium hydroxide could be grouped in another column. The same could be done for all the other elements with their own unique common properties.

      Once the elements had been laid out, it was possible to see where the gaps in the table were (elements not yet discovered at the time), and to even predict their chemical properties.

      Now that we know about the atomic structure of atomic nuclei (protons & neutrons) and understand the different energy levels for electrons (their orbitals/shells), we can see that the periodic table also corresponds to how many electrons are in each orbital.

    • Photo: Bernice Ridley

      Bernice Ridley answered on 22 Mar 2023:

      The periodic table is a way of grouping elements together to show elements that have similar properties (groups), this means that scientists can predict how elements can react without having to do lots of experiments. The new elements that have been synthesised tend not to exist for very long as they are so big they will be radioactive and break into other elements and are prepared on a tiny scale. Hence, it isn’t possible to check very much about their properties. Some reactions are too explosive to carry out in a lab so predictions help. The rows of elements are in increasing mass and are linked to the outermost electrons (in shells, orbitals or clouds dependent on whether you are at GCSE, A-level or degree level!) and this is why it is a weird structure with drop-down bits. I had to know the periodic table off by heart when I was at university, I probably couldn’t write it out now but I hope I’d get most of the top three or four rows!

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