How does the octet rule affect metals?
1 Answer
The octet rule for says that Main Group metals (those in Groups 1 and 2) will react to get eight electrons in their outermost shell.
The Main Group metals achieve their octet by donating their valence electrons to nonmetals. This exposes their octet of valence electrons in the next lower level.
The metals in Groups 3 to 12 can obey the octet rule, but they are not required to do so. They have d electrons that they can use to put more than eight electrons in their valence shell ("expand their octet").
For example, Fe has the electron configuration [Ar]4s²3d⁶. It can lose the outermost 4s electrons to form FeCl₂, but it can also lose a 3d electron to form FeCl₃.
Metals in Group 13 tend to form covalent compounds. A molecule such as AlCl₃ has only six valence electrons. It violates the octet rule.
Metals in Groups 14 to 16 can obey the octet rule, but they do not have to use all their valence electrons.
For example, Sn has the configuration [Kr]5s²4d¹⁰5p². It can use its four outermost electrons to form SnCl₄ or only the 5p electrons to form SnCl₂.
