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Name: tom hammargren
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: 1999 


Question:
I've heard that atoms or ions try to get eight electrons in their valence shells and by doing so they become more stable and unreactive. I don't hear about WHY, when the octet rule is obeyed, atoms or ions are more stable and less reactive. For example, is neon unreactive for reasons more than simply the s and p subshells are filled with eight electrons?



Replies:
An excellent question, tom...basically, the octet rule is a simple way of rationalizing why the first two rows of the periodic table behave the way we do. It is not a "law of nature," but rather a "rule of thumb" which, when applied, does have some predictive power. Another way to think of the octet rule is as an "organizing principle," which means that it organizes a lot of data into one simple idea by observing patterns in experimental data such as atomic ionization energies, electron affinities, etc. But there are many exceptions to the octet rule... Fundamentally, since atoms are quantum-mechanical objects, one needs to apply the "full force" of quantum theory to begin to grasp the reasons why an octet is a relatively stable way to be. These have to do with the special properties of electrons, which as spin=1/2 particles, find it energetically advantageous to be able to change places with other electrons once in awhile, but only if they have the same "spin"...an amazing effect known as fermion exchange. However, this is counterbalanced by the fact that the electrons repel one another electrically...taking both of these into account, one can rationalize most of the periodic table (at least the first few rows).

To explain further, I'd have to ask you to sit in on the university course I teach in general chemistry. Maybe you'll consider just taking such a course yourself..?

- best wishes, topper



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