Should chlorine be in group 31?

Thursday 28 February 2019

The 150th anniversary of Mendeleev’s periodic table has catalysed many chemists to question all the different ways in which the elements can be arranged to maximise the usefulness of the table.  A good article on this by Joshua Howgego has appeared in the New Scientist.

Since elements are currently ordered in terms of atomic number many people think that logically the elements should be arranged to give 32 groups.

The long form of the periodic table (source

In the last IB chemistry curriculum chlorine was located in group 7. In the current programme it is in group 17. Maybe in the next programme (which has now been been officially delayed so that the first exam is now in May 2024 instead of May 2023) chlorine will find itself in group 31?

Comments 1

John Battaglino 13 March 2019 - 13:19

I think the IB gets too involved in nit-picky conventions and nomenclature (+2, 2+) (van der Waals/Londond Dispersion) (dative or coordinate covalent) (STP-22.4/22.7), I think its more important to know where Chlorine's relative position in the table is and why,.... we can all make tables where we put the Lanthanide and Actinide series where they belong. I actually think this exercise is informative. More consideration should be given to what belongs in standard and high level, NOT based upon what universities want, but what good pedagogy says is effective, especially as regards developmental learning among high school students. Since many chemistry students will either NOT have chemistry again,... or will have it at the university level, I would much rather them actually understand the chemistry, than just have a formulaic way of using sophisticated ideas or analytical methods. (okay,. time to get off my soap box. :-) )

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