MadSci Network: Chemistry |
Hello,
The octect rule applies well to the first three rows of the periodic table (from Hydrogen to Argon - it also works well with Potassium and Calcium). However, once you start to consider transition metals (or any element starting with Scnadium), orbitals other than s and p need to be taken into account to explain observed reactivity and other properties. The transitions metals such as Iron have access to d orbitals, which can hold up to 10 electrons.
So Iron has 8 electrons in it's valence shell and they are arranged with two electrons in an s orbital and 6 in a d orbital. Because the d orbital can hold up to ten electrons and only has 6, it is not yet full and so iron does not act like a noble gas.
Electron configuration involving d orbitals (some elements even have f orbitals which can hold 14 electrons!) is usually discussed in high school chemistry classes and introductory college chemistry courses. You can go to the Los Alamos National Lab periodic table website, which gives the electron configuration of every element on the periodic table: http://periodic.lanl.gov/default.htm
In addition, any high school level text book will give fundamentals for arranging electrons. This is usually reffered to as the Aufbau principle.
Try the links in the MadSci Library for more information on Chemistry.