I like many kinds of periodic table, but hate this one. See the problem?
Element 57 is drawn right next to element 72, replacing the element that should be there: element 71. So lutetium, element 71, is being denied its rightful place as a transition metal and is classified as a rare earth. Meanwhile lanthanum, element 57, which really is a rare earth, is drawn separately from all the rest! This is especially ironic because those rare earths are called ‘lanthanoids’ or ‘lanthanides’.
Similarly, element 89 is next to element 104, instead of the element that should be there: element 103. So lawrencium, element 103, is also being denied its rightful place as a transition metal. Meanwhile actinium, element 89, is banished from the row of ‘actinoids’, or ‘actinides’ — even though it gave them their name in the first place. How cruel!
Here Wikipedia does it right. Element 71 is a transition metal — not element 57. Similarly element 103 is a transition metal, not element 89.
This stuff is not just an arbitrary convention. Transition metals are chemically different from lanthanides and actinides. You can’t just stick them wherever you want.
In simple terms, as we move across the transition metals, they fill 1, 2, 3, … , 10 of their outermost d orbitals with electrons. Similarly as we move across the lanthanides or actinides, they fill 1, 2, 3, … 14 of their outermost f orbitals with electrons. I wrote about this here a while ago:
• John Baez, The Madelung rules, Azimuth, December 8, 2021.
There are some exceptions to the Madelung rules, but the bad periodic tables are not motivated by those exceptions. The Wikipedia periodic table accurately reflects the chemistry. The Encyclopedia Brittanica table completely ruins the story by arbitrarily sticking lanthanum and actinium in amongst the transition metals instead of the elements that should be there: lutetium and lawrencium. I see no good reason for doing this.
Here’s another common kind of periodic table that I hate. It cuts a hole into the bottom two rows of the transition metals, and moves the metals that should be there — elements 71 and 103 — into the rare earths and actinides.
This amounts to claiming that there are 15 rare earths and actinides, and just 9 transition metals in those two rows. That’s crazy: the fact that the p subshell holds 10 electrons and the d subshell holds 14 is dictated by group representation theory. Subshells hold 2, 6, 10, 14 electrons — twice odd numbers.
The periodic table is a marvelous thing: it shows how quantum
mechanics and math predict patterns in the elements. Have fun making up new designs — but if you’re going to use the old kind, use the good one!
If you don’t believe me, listen to this guy:
But unlike him, I don’t think experiments were necessary to realize that the bad periodic tables were messed up. It’s not as if they were designed based on some alternative theory about which elements are transition metals.
Interestingly, the International Union of Pure and Applied Chemistry were supposed to meet at the end of last year to settle this issue. What did they decide? If you find out, please let me know!