Where are the lanthanides and actinides placed in the periodic table? Why?

1 Answer
Jan 28, 2017

Answer:

You mean to ask why the lanthanides and actinides are placed in a separate section of the Periodic Table.

Explanation:

Both the lanthanide and actinide metals are LARGE, Lewis-acidic metals, in which the #f# subshell is progressively filled. The Group 3 metals, scandium, yttrium, and lanthanum, are often considered in this category, because they share similar chemistry.

Given the properties of the #"f-orbitals"# (which are diffuse, and offer poor electronic shielding), the f element metals usually give #M^(2+)#, and #M^(3+)# oxidation states, and are marked by extreme Lewis acidity. Their chemistry is the province of specialists.