From Wikipedia, the free encyclopedia
IUPAC has not recommended a specific format for the periodic table, so different conventions are permitted and are often used for the group number of lanthanides and actinides. There is no pre-existing physical entity for a "group" of elements. The notion is simply a convenient classification, since some elements have similar periodicities in their properties. This allows them to be arranged in columns that also happen to correspond with electron configurations.
- Some tables [2] include lutetium, (Lu) and lawrencium, (Lr) in group 3. These elements terminate the lanthanide and actinide series, respectively. This is the arrangement preferred by Glenn T. Seaborg. Since the f-shell is nominally full in the ground state electron configuration for both these metals, they behave most like d-block metals out of all the lanthanides and actinides, and thus exhibit the most similarities in properties with Sc and Y. For Lr, this behavior is expected, but it has not been observed because sufficient quantities are not available. (Also see Periodic table (wide) and Periodic table (extended).)
Some tables [3] refer to lutetium, lawrencium, and all lanthanides and actinides by a marker in group 3. A third and fourth alternative are suggested by this arrangement:
- The third alternative is to regard lutetium, lawrencium, and the entire 28 lanthanide and actinide elements as included in Group 3. Lanthanides, as electropositive trivalent metals, all have a closely related chemistry, and all show many similarities to Sc and Y.
- The fourth alternative is to exclude lutetium, lawrencium, and the lanthanides and actinides from group 3. The lanthanides possess additional properties characteristic of their partially-filled f orbitals which are not common to Sc and Y. Furthermore, the actinides show a much wider variety of chemistry (for instance, in range of oxidation states) within their series than the lanthanides, and comparisons to Sc and Y are even less useful.
[edit] External links
