Note Ive put the debate at TalkYttrium in the next section so that lazy editors dont  have to click the link to see what he is talking about  edit Periodic group Surely the group  elements are Sc Y  La Ac NOT Lu See for example longform periodic table Petergans talk   Both conventions are common and are often a source of debate The group  element article tries to explain the story Itub talk   Common Ive never seen it Lu is a lanthanide in all the standard inorganic texts Greenwood  Earnshaw Cotton  Wilkinson Housecroft  Sharpe Shriver  Atkins  The debate was concluded long ago Petergans talk   Just last month there was an article published in J Chem Ed continuing the debate advocating La and Ac in group  and it cites a few books and articles that follow the opposite convention See  There are also four letters about this topic in the same issue Itub talk   Unbelievable In  years as a chemist I have never until yesterday seen a periodic table with Lu anywhere other than in the lanthanide series Web elements is a first for me and as far as Im concerned just another example of nonsense on the web IUPAC puts La under Y There is no ambiguity about it just that the lanthanide series convertionally starts with La and is usually written separately Petergans talk   This is not nonsense on the Web There have been many textbooks published since the s that put Lu under Y I cant say whether they are the majority or the most influential Just one example Wulfsbergs Inorganic Chemistry Wulfberg explains his reasoning in a footnote In this letter to JCE the authors looked at  textbooks for what they call flyleaf periodic tables If you look at the figure in the letter among the textbooks published since   put La under Y  put Lu and  put all  lanthanides like IUPAC IUPACs table is ambiguous It doesnt put any specific element under Y it puts all the lanthanides there Itub talk   Im flabbergasted I thought elements were put in the same group because they have the same electronic configuration The trivalent ions of Sc Y La Ac have a noble gas electronic configuration LuIII does not How can it be put in the same group Dont answer that I stand by the word nonsensePetergans talk   Ill dare to answer despite your request Im relatively neutral on this issue because I think it is largely an arbitrary convention but I enjoy playing devils advocate  the periodic table predates knowledge of electronic configurations and sometimes exceptions are made in the name of chemical properties or even in the name of layout in my opinion such as putting helium above neon instead of above beryllium although some tables do put He above Be  the relationship between the electronic configurations of Y and La is essentially the same as the one between Al and Ga Al and Ga are both sp but Ga has a full d shell that Al doesnt have Y and Lu are both sd but Lu has a full f shell that Y doesnt have Trivalent Lu also has a noble gas configuration in the sense of having no s and p electron in the valence shell same as trivalent gallium  if one looks at the neutral atom La has the same configuration as Y but thats an anomaly in that it doesnt follow the aufbau rule But we dont move elements such as copper and palladium to another group just because they happen to deviate from aufbau Finally one slight disadvantage of putting La under Y is that you end up with a discontinuous d block in the long form of the periodic table which looks a bit odd in my opinion Itub talk   no indent The counter to that argument is that in the spirit of Mendeleev elements a grouped together because of similarities in chemistry Therefore it is the electronic configuration in the group oxidation state that counts not the configuration of the atoms Cu is the classic example Arsd in the atom but in CuI the relative energies of s and d are reversed and it is the s electron which is lost on oxidation of the metal so Cu sits comfortably in a group with Ag and Au For Au the f electrons are discounted as they belong to the filled shell comprising s p d and f  We can argue this one for ever but what concerns me now is that the basic image of the longform periodic table which is used in WP for all the elements puts Sc and Y above Lu and presents La and Ac as a group on their own I believe that this is misleading as it does not clearly distinguish the lanthanide and actinide series from the maingroup elements and transition metals longform periodic