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
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
- Atoms with an empty d-sublevel can expand their octet to 10 or 12 electrons if necessary.