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Atomic radius and Ionization Energy Trends?

  1. Feb 23, 2016 #1
    My teacher was not too clear about this and from what I've gathered is if you're given two elements this is how you would figure out which one has a larger atomic radius or ionization energy, but I'm not sure if it's accurate

    Radius: Whichever one is in a lower period (more energy levels) has a larger radius, if they're in the same period whichever one has the lower atomic number has a larger atomic radius
    I.E - Whichever one is in the higher period (less energy levels) has more ionization energy, if they're in the same period the one with the higher atomic number is higher

    Also, are Electronegativity and I.E the same thing except noble gases have an electronegativity of 0?
  2. jcsd
  3. Feb 24, 2016 #2


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    Staff: Mentor

    You should be able to easily find raw data (for example just google for periodic table trends atomic radius) and they will either confirm, or deny what you wrote.

    To (mis)quote or paraphrase Feynman - in the end it is data (nature) that is right, doesn't matter what we think or predict.
  4. Feb 25, 2016 #3
    Hey there,

    For the radius, whichever atom has the most electrons is the biggest. However, if you have two atoms with the same number of electrons, the atom with the LEAST PROTONS is the biggest. Ionization Energy is how much energy is required to remove an electron, so atoms with a full octet will require the most energy in order to remove an electron. So the more valence electrons = more I.E required.

    Also, no, electronegativity and ionization energy aren't the same thing. Electronegativity is the attraction due to different charges.
  5. Feb 25, 2016 #4


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    Staff: Mentor

    Not necessarily. Check radii of lanthanides.
  6. Feb 26, 2016 #5
    Actually this holds well till we reach the f-block elements. Post this, the phenomenon of lanthanide contraction dominates and we observe deviations. Just like Borek said.
  7. Feb 26, 2016 #6


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    You do that thing. It's a matter for your judgment whether the data you will find could be called 'raw'. Until you understand how the conclusions called 'data' have been arrived at it is not fully scientific.

    Here is an official explanation of the results, though not how they were obtaine, and you can find many others like it:. https://www.khanacademy.org/science...ic-table-trends-bonding/v/atomic-radius-trend

    If you are intending to go much further in chemistry (or atomic physics) then I advise: always connect. Ionisation is the special extreme case of promotion or increase of energy of an electron. The more general case is jumping between different levels within the atom. If you have got at least as far as the Bohr atom, then Google for Mosley's law, and pick among what comes out according to your level.
  8. Mar 1, 2016 #7
    The Chemical Touch app, is an excellent reference for this sort of stuff and only costs a dollar and a half. There's also the free Merck PTE app that has this information laid out in a very elegant graphical form and it's free without ads!
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