• Question: what is the point of the period table ?

    Asked by tyffani to Daniel, Jon, Louise, Sharon, Zoe on 16 Jun 2010 in Categories: .
    • Photo: Louise Dash

      Louise Dash answered on 14 Jun 2010:

      It looks great on a mug!
      http://www.amazon.co.uk/MS-Mugs-Periodic-Table-Large/dp/B0015QT5YK
      What more of a point could you want? 😀

      Seriously though, the periodic table is incredibly useful – from a physicist’s point of view it tells you at a glance how many electrons are in an atom’s outer shell. Chemists use it to work out which elements will combine to make compounds. Because of the way it’s arranged in rows and columns, you can tell which elements are likely to behave similarly – the elements in each column generally have similar properties. Neon, for example, is an inert gas with a full outer shell of electrons (you can tell because it’s in the far right column). The periodic table tells you that other elements from the same column, like Argon and Krypton, will also have very similar chemical properties.

    • Photo: Jon Copley

      Jon Copley answered on 15 Jun 2010:

      Before the periodic table came along (it was figured out by Dimitri Mendeleev in 1869), chemistry was frankly a mess. No-one could reliably predict how different elements would react or behave. What Mendeleev did was to organise the chemical elements according to their properties. So elements in the same column of the table tend to react and behave in a similar way.

      For example, the left-most column in the table are the “alkali metals” – and these tend to explode if you throw them in water (one of my favourite experiments at school was thowing a lump of potassium into a swimming pool – huge bang and flash, and then what was left of the chunk raced about the surface of the pool fizzing violently). So everything in the first column of the table is very reactive. In contrast, the right-most column are the “noble gases”, and they don’t react much with anything.

      So what is it that makes something go in a particular column? It turns out that the position of an element in the table depends on its atomic structure. Each row of the table represents a “shell” of electrons around the nucleus of the atom. So elements in the first row (hydrogen and helium) only have one shell of electrons around their atomic nucleii. Elements in the second row have two shells (a bit like the layers of an onion), and so on.

      What makes elements in the left-hand column very reactive is that they only have one electron in their outermost shell. So there is plenty of “space” in that shell for interactions with electrons in the outer shells of other elements – and that makes the “alkali metals” highly reactive.

      And what makes elements in the right-hand column of the table very unreactive is that their outer shells are full of electrons. So there is no “space” for interactions with electrons in the outer shells of other elements – and that makes the “noble gases” very unreactive.

      So if you know where an element sits in the periodic table, you can predict how it will react and behave – and also what its atomic structure will be. The periodic table brought order to the chaos of chemistry that had lasted for centuries before. If you want to predict how two elements will react together (for example in chemical engineering), you can use the periodic table to figure it out.

    • Photo: Zoe Duck

      Zoe Duck answered on 15 Jun 2010:

      The periodic table gives us information about over 100 elements found in the universe. Everything is made up of one or more of these elements.

      Each element is made of a specific atom with a certain number of protons and neutrons in the nucleus, orbitted by electrons. The periodic table tells us how many protons and neutrons are in each element.

      Each row and column of the table has a pattern- each column contains elements with the same number of electrons in the outer energy level. Each row contains elements with electrons in the same energy level with numbers increasing from left to right.

    • Photo: Sharon Sneddon

      Sharon Sneddon answered on 16 Jun 2010:

      ooh, I don’t think I can add anything to those great answers!! I’m too late!!

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