Tuesday, May 17, 2011

The Out of this World Octet Rule!

Q: What is the out of this world octet rule?
A: The octet rule states that in forming compounds, atoms tend to achieve the electron configuration of a noble gas (*they do NOT actually become a noble gas*) 

  • an octet is a set of eight. 
  • noble gases except He have eight electrons in its highest energy level. 

a. "atoms of metals tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of some non-metals tend to gain electrons or to share electrons with another nonmetal to achieve a complete octet."

  • recall that a valence electron is an electron in the highest occupied energy level of an atom.
    • s and p orbitals are considered the valence electrons (note: 2 electrons in the s orbitals, and 6 in the p orbitals)
    • Beginning with the n=3 principle quantum number, the d orbitals become available.
b. Exceptions to the octet rule: 
1. Molecules with an odd number of electrons
Ex: There are 5 valence electrons around the nitrogen. A double bond would place 7 around the nitrogen, and a triple bond would place 9 around the nitrogen.
 unable to get an octet around each atom.


2. Molecules in which an atom has less than an octet
Ex: BF3

  • commonly seen between Boron and Beryllium)












3. Molecules in which an atom has more than an octet
  • Third period elements sometimes exceed the octet rule by using their empty d orbitals to accommodate additional electrons


    c. 
    • Atoms with an empty d-sublevel can expand their octet to 10 or 12 electrons if necessary.
      • Third period elements sometimes exceed the octet rule by using their empty d orbitals to accommodate additional electrons

    2 comments:

    1. 2 things:

      1. for exceptions to the octet rule and not gaining a full octet, you mentioned B and Be, but nitrogen can also not gain a full octet

      2. the first two bullet points of the post sound like something from an instant word power session (with the bold eights being the blanks)

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    2. Emily!!! Great job with your blog it is very organized and detailed. I also I love how you included pictures to explain your question. However, I agree with sahil's first point from above. Also, I might have explained some of the terms from the first trimester, such as what the s and p orbitals are and about the quantum numbers. Over all you did a great job and your blog was very informative!!

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