• Question: Who elements have atomic numbers?

    Asked by paulfee1 to Cathal, Ciara, Emma, Michael, Sive on 14 Nov 2013.
    • Photo: Sive Finlay

      Sive Finlay answered on 14 Nov 2013:

      Hi Paul,
      Every element has an atomic number, that’s what makes them elements! The atomic number is the number of protons found in the nucleus of an atom. Each element has a different number of protons which gives them different chemical properties and makes them unique elements.
      Sive

    • Photo: Michael Nolan

      Michael Nolan answered on 14 Nov 2013:

      I guess you mean why?

      It is a way to systematise the 92 naturally occurring elements and Sive is right about where it comes from. Originally, the elements were ordered by weight, but due to the presence of neutrons this measure does not always work. So when Mendeleev created his periodic table, he work instead with the number of protons, the atomic number, and had to make some changes. He was also able to use the atomic numbers to spot gaps, e.g. germanium was not known to his era, but he made a space for it. THe same for gallium.
      The atomic number is also the number of electrons in the neutral element.

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