• Question: Is there a certain way to count the protons in an element when identifying them? Or do you determine them from the number of electrons? If so how?

    Asked by joy8511 to Andrew, Beth, Bruce, Lindy, Lizzie on 14 Jun 2012.
    • Photo: Lindy Heath

      Lindy Heath answered on 14 Jun 2012:

      If you take a look at the periodic table, the atomic number (the little number in the top left of the box) is the same as the number of protons in the element. An element is made up of atoms and these atoms are made up of protons, neutrons and electrons. Protons are positively charged, neutrons are neutral (display no charge) and electrons are negatively charged. Overall, an atom is neutral which means that there must be the same number of protons and electrons (so that the charges cancel each other out). So you can get the number of protons and electrons in an element by looking at the atomic number. For example, carbon has an atomic number of 6 which means that it has 6 electrons and 6 protons.

    • Photo: Bruce Alexander

      Bruce Alexander answered on 15 Jun 2012:

      There is a technique called mass spectrometry that is pretty good at counting protons, albeit indirectly.

      If you take an element, and strip of an electron you make it slightly positively charged. If you ping it through a gap between two oppositely charged plates (one negatively charged, and one positively charged), then the positively charged element will be repelled by the positive plate and attracted to the negatively charged plate. How fast the element moves towards the negative plate depends on how heavy the element is and, as the weight of an element depends on how many protons it has (as well as neutrons) you can “count” the number of protons by measuring how fast the element moves towards the negative plate.

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