Ionization Energy

Discussion in 'Chemistry' started by chikis, Feb 8, 2012.

  1. chikis Registered Senior Member

    Messages:
    328
    When it comes to defining, explaining, expressing, discussing and telling what ionization energy is, many give variety of defination, explaination, expression, discussion and teaching from different angles but still arriving at the same point thereby confusing some learners like me at the end of the whole show. My question to this great honourable forum is this:
    What is the exact and precise defination to the term ionization energy?
    Another question:
    It is known and widely accepted fact that ionization energy generally decreases steadily down a given group and increases from left to right, what does that mean? How can I visualize it (the statement) for a better understanding?
    So folks, what do you have to say about the above questions?
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. origin Trump is the best argument against a democracy. Valued Senior Member

    Messages:
    9,821
    definition

    Periodic table and ionization energy
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. arauca Banned Banned

    Messages:
    4,564


    I believe is contrary to what you mentioned , As you move from group l to group ll the ionization strength increase Say Li ionization 5. ev Be 9.2 ev F 17 ev.
    As you go down in group th ionization decreases fron Li 5. ev Rb 4.1 ev
    in this case the distance from the nucleus shows its effect.
    Hope it helps
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. chikis Registered Senior Member

    Messages:
    328
    which is contrary to what I mentioned?
     
  8. arauca Banned Banned

    Messages:
    4,564
    "ionization energy generally decreases steadily down a given group and increases from left to right


    First electron to ionize ( Li 5.0 electovolt) F 17 .0 electrovolt this is going from group l to group Vll

    Now if you say on the same group l from lithium to Cs. then there is a decrease in ionization strength. Uf this is what you meant I agree with you . In this case my explanation would be : there is a steady increase in electrons in the element from on period to the next . So two things affect the distance from the nucleus and the other is the electron cloud density which increases with period and that will reduce the bond strength the outer electron to the nucleus.
     
  9. Nasor Valued Senior Member

    Messages:
    6,221
    It's mostly because electrons don't do a very good job shielding other electrons with the same principal quantum number, so as you add more electrons to orbitals with the same principal quantum number (meaning going left to right across a period), the valence electrons "see" more positive charge from the nucleus, and so are more strongly attracted, meaning the ionization energy goes up.
     
  10. leopold Valued Senior Member

    Messages:
    17,455
    it's the voltage needed to strip electrons from their parent atoms.
    it's probably directly related to the dielectric constant of the material in question.
     
  11. Aqueous Id flat Earth skeptic Valued Senior Member

    Messages:
    6,152
    I wouldn't have thought of that, because if I was working in pure theory, in the periodic table, or just looking at the orbitals, and the electron potential at each level, I would have overlooked that the material is what I really have to work with. But the material itself has organic properties - like the intrinsic conductivity, and this, the dielectric constant, too. And there's a field theory behind getting it to go into emission, in which even the shape affects where the field breaks down, so this is yet another level for analysis. Hmmm. So that's why they have a lab section to go with the lecture.

    Those are the really tough questions, though, where you try to account for the empirical result not matching your theoretical prediction.
     
  12. Aqueous Id flat Earth skeptic Valued Senior Member

    Messages:
    6,152
    So do you understand the basic concept of ionization energy? You sound like you are looking for a very basic understanding. Do you think you have a handle on it now?
     
  13. chikis Registered Senior Member

    Messages:
    328
    Well, I think am catching it gradually but in the course of my research, I will forward in more questions and contributions concerning the thread. Thank you!
     
  14. chikis Registered Senior Member

    Messages:
    328
    Since noble gases have large atomic radius, are they not suppose to have low ionization energy? The reason being that thier valence electron will be very far from the nucleuos attraction. That means only small amount of energy will be required in removing it (the valence electron).
     
  15. chikis Registered Senior Member

    Messages:
    328
    I was going through my past question and answer, I then came across this:
    "The noble gases have the highest ionization energies in each period".
    I then wondered why and how the above statement is a reality. How can the above statement be true when the noble gases have large atomic radi?

    I know that Ionization energy, is the energy required to remove the outermost electron from a gasous atom.
    If you say that the noble gases has the highest Ionization energies, how true is that when you know that the noble gases have a relatively large atomic radius?
    I belive that the noble gases should have the lowest ionization energy since they have large atomic radius. This (lowest ionization energy) is possible because the larger the atomic radius the farer the distance of the outermost electron from the attraction of the nucleuos, thereby making it easier for outermost electron to escape. In such circustance, the outermost electron will leave with a very small energy.
    From my statement above, I have it that the noble gases have the lowest and not the highest ionization energy.
    If you the person viewing this my thread has a contrary view to mine on this concept on discusion feel free to share your own opinion. Let's see how we can collectively solve this problem.
     
  16. Aqueous Id flat Earth skeptic Valued Senior Member

    Messages:
    6,152
    If you look at a graph of the first ionization energy as a function of atomic number it is not a straight line, as one might think at first, and there are sharp peaks at each of the noble gasses.

    In fact, the reason they are even noble gasses is directly related to these peaks. It takes so much energy to ionize them, that they tend to remain inert (pure atoms, not forming compounds). And this is because there shells are completely closed (full of electrons). This means they have achieved electrical neutrality, so they don't already tend one way or the other (to accept of donate electrons).

    If you look at their names you will also recognize some of them as the names of flourescent lighting. This is because the energy level to ionize them is sharp enough that they will tend to fall back into stability and emit a photon in the process. Basically, the flourescent lamp puts them into emission, but they don't stay energized, they fall back, emitting an electron, then are quickly re-energized by the heat in the bulb and this they oscillate back and forth between high and low energy states, constantly emitting photons.

    As you will see, nearly all the properties of materials arise from the character of the outer shell. For the noble gasses, it's a tendency to stay electrically neutral, with the shells full, to resist ionization, and to avoid bonding, which is precisely why they exist as gasses in nature.
     
  17. Aqueous Id flat Earth skeptic Valued Senior Member

    Messages:
    6,152
    Yes it turns out that atomic radius in itself is not nearly as important as whether the atoms have achieved electrical neutrality.

    If you look at a graph of the first ionization energy as a function of atomic number it is not a straight line, as one might think at first, and there are sharp peaks at each of the noble gasses.

    In fact, the reason they are even noble gasses is directly related to these peaks. It takes so much energy to ionize them, that they tend to remain inert (pure atoms, not forming compounds). And this is because their shells are completely closed (full of electrons). This means they have achieved electrical neutrality, so they don't already tend one way or the other (to accept of donate electrons).

    If you look at their names you will also recognize some of them as the names of flourescent lighting. This is because the energy level to ionize them is sharp enough that they will tend to fall back into stability and emit a photon in the process. Basically, the flourescent lamp puts them into emission, but they don't stay energized, they fall back, emitting an electron, then are quickly re-energized by the heat in the bulb and this they oscillate back and forth between high and low energy states, constantly emitting photons.

    As you will see, nearly all the properties of materials arise from the character of the outer shell. For the noble gasses, it's a tendency to stay electrically neutral, with the shells full, to resist ionization, and to avoid bonding, which is precisely why they exist as gasses in nature.
     
  18. chikis Registered Senior Member

    Messages:
    328
    Is because all noble gases has attain octet structure and cannot loose electron from their outer most shell that they all have high ionization energies?
     
  19. origin Trump is the best argument against a democracy. Valued Senior Member

    Messages:
    9,821
    Nice post.

    Please Register or Log in to view the hidden image!

     
  20. Aqueous Id flat Earth skeptic Valued Senior Member

    Messages:
    6,152
    @Origin

    Coming from you this truly a compliment. Thanks.

    Please Register or Log in to view the hidden image!



    @chikis

    I goofed in the middle of my last post when I said they emit an electron. I meant to say photon. First comes electron emission then an electron is captured to fill the vacancy and this causes a photon to be emitted.


    They all have an octet except of course Helium. I think it will help more to think of this in terms of electrical charge. These are electrically neutral atoms. When you strip one away from eight, it leaves 7 charges behind which is highly negative. You must overcome the difference between neutrality (zero net charge) and this highly negative condition, so that takes more energy than any neighboring atom might require to strip one away.
     
  21. chikis Registered Senior Member

    Messages:
    328
    Is helium not a noble gas? Why are you puting it as exception?
     
  22. Aqueous Id flat Earth skeptic Valued Senior Member

    Messages:
    6,152
    Yes, it is a noble gas which is why I mentioned it. I was just pointing out that it stands alone (in the upper right of the periodic table) because it's too small to have 8 electrons. Its atomic number is 2, so it only has 2 electrons.
     
  23. Nasor Valued Senior Member

    Messages:
    6,221
    Good lord...
    No. Noble gases have SMALLER atomic radii. Which is part of why they have such high ionization energies. http://www.grandinetti.org/Teaching/Chem121/Lectures/AtomicRadii
    Ionization energy is proportional to charge, but it's proportional to the square of the radius...so a change in atomic radius generally matters more than a change in charge. It takes less energy to go from Mg+1 to Mg+2 than it does to go from neutral Ar to Ar+, because Ar has a smaller radius.
    Really? It takes more energy to ionize Cl than to ionize Xe, yet Cl is very reactive and Xe is not...clearly ionization energy is not a great predictor of reactivity.
    You appear to be saying that having a full shell means that an atom is electrically neutral, which is wrong. But perhaps you simply meant that they are both electrically neutral and have a full shell.
    No. The photons in a fluorescent light are emitted by mercury atoms, not the noble gases. The purpose of the noble gases in a fluorescent bulb is to completely lose electrons, providing electrons that will be accelerated by the voltage in the lamp and slam into the mercury atoms so that the mercury atoms emit light. If the electrons on the excited noble gases were prone to falling back to their parent noble gas nucleus by emitting a photon (rather than being stripped away to fly off and hit a Hg atom), the lamp wouldn't work because there wouldn't be any free electrons to fly around and bang into the mercury atoms.
    No it wasn't.
    Still wrong...

    Edit: fixed typo
     
    Last edited: Mar 16, 2012

Share This Page