Ionization Energies: Exploring the Physics Behind Odd vs. Even Electrons

In summary: Yes, there is a quantum physics explanation for this. The electrons in a shell are filled according to quantum mechanics rules. So, in summary, the most stable configuration is usually either a filled or half-filled orbital. As you add more electrons to a shell, the shielding effect increases, which decreases the ionization energy.
  • #1
warrior_1
11
0
This question is not a homework question. I am having a little trouble with the ionization
energy graph. I understand that the noble gasses are the most stable
and hence require the most energy to be ionised, but why is it that after you
add even number of electrons the ionization energy increases but when it
is odd numba of electrons the ionization energy decreases. I understand that as you add shells the sheilding effect increases, but why is it that when you add an odd number of electrons the ionization energy decreases??

Is it because when electrons are in pairs they are more stable?? What is the nuclear physics or qunatum physics explanation behind this


Thanks in Advance
 
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  • #2
The most stable configurations tend to be either filled or half-filled orbitals. I'm not sure where you are getting that even numbers of electrons are necessarily more stable than odd numbers.

For example, nitrogen (7 electrons) has a higher IE than oxygen (8 electrons). This is due to the stability of a half-filled 2P shell for nitrogen.

For example, see the table here:
http://dl.clackamas.cc.or.us/ch104-07/ionization_energy.htm [Broken]
 
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  • #3
But u can see in that figure, once u add an extra electron after the shell is filled it automatically drops off right, once u add the second the ionization energy increases, once you add the third it drops off again... i obviously don't understand what's going on here so by no means am i saying I am right about what i said, i just want to know how it all works.
 
  • #4
Okay, I think I can give a more helpful explanation now.

Have you learned about S orbitals and P orbitals? The important thing to know is that S orbitals need only 2 electrons to be filled, while P orbitals need 6 electrons.

So, looking at what happens after neon, for example: neon has a filled P orbital, so the next element (Na) has a drop in ionization energy. Two elements past neon is Mg, which now has a filled S orbital -- because S orbitals need only 2 electrons to be filled. Because of it's filled orbital, Mg has a higher I.E. than the elements next to it.

The next element after Mg is Al, at which point we are adding electrons to P orbitals, and it takes 6 more electrons to fill that. These filled orbitals are filled 6 elements after Mg, or at Ar. So Ar has a high I.E. again. Also, note that when the P orbitals are half-filled with 3 electrons, at P (Z=15 on the graph), there is a slight rise in I.E. there. Half-filled orbitals are also stable, though not as stable as filled orbitals.

Hope you're able to follow all this on the graph I linked to before.
 
  • #5
But is there a quantum physics explanation for this. As this is for a physics course, and they don't really go into how many electrons fill a shell etc, i understand what ur talking about coz I've done chem b4 but this is for a quantum mechanics course.
 

1. What is ionization energy?

Ionization energy is the amount of energy required to remove an electron from an atom or molecule in its gaseous state. This process results in the formation of a positively charged ion.

2. How is ionization energy measured?

Ionization energy is typically measured in units of electron volts (eV) or kilojoules per mole (kJ/mol). It can be experimentally determined by subjecting a sample of a gas to high-energy radiation and measuring the resulting ions.

3. What factors affect ionization energy?

The main factors that affect ionization energy include the atomic or molecular structure, the nuclear charge, and the distance between the nucleus and the outermost electrons. As the nuclear charge increases and the distance between the nucleus and electrons decreases, the ionization energy increases.

4. Why do odd and even electrons have different ionization energies?

Odd and even electrons refer to the number of electrons in an atom or molecule. Atoms or molecules with an odd number of electrons tend to have lower ionization energies compared to those with an even number of electrons. This is because the odd electron creates an unpaired spin, making it easier to remove due to its higher energy state.

5. How does ionization energy relate to chemical reactivity?

The ionization energy of an atom or molecule is closely related to its chemical reactivity. Elements with low ionization energies are more likely to form chemical bonds and undergo reactions, while those with high ionization energies are more stable and less reactive. This is because it requires more energy to remove an electron from a highly charged atom, making it less likely to participate in chemical reactions.

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