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.
