Hi. So what’s this?
OK, so it would have been a better question had the answer not been in the title of the post… But you would have known this was a Periodic Table anyway, right? And that’s quite amazing from just the outline (no details) of what is just a series of rectangles (or one rectangle with some missing bits). This shape has become quite iconic, and recently not just in chemistry. It has been appropriated for all sorts of applications, wherever people want a strong graphical image to represent a list of related objects. So a quick search reveals:
- A periodic table of vegetables
- A periodic table of fruits and nuts
- A periodic table of books
- A periodic table of internal communications
- A periodic table of swearing
And indeed, here is an article called ‘The Periodic Tables of Everything But Elements’. These are obviously frivolous items, and no criticism of them is intended. But if they can appropriate the periodic table for amusing ends, we can do the same back to make a (half-)serious point!
Right, two things. Firstly, apologies to fans of the lanthanides and actinides – you are often un-catered-for… Here’s a periodic table (of the elements, not biscuits or whatever), with all the information stripped out except the atomic numbers.
The lanthanides (58 – 71) and actinides (90 – 103) are the block down at the bottom. They really do exist, and yet are often missed off ‘other periodic tables’ for graphical purity or some such. Poor elements. They are about 25 % of the Periodic Table!
Secondly, the lanthanides and actinides genuinely are a block of their own. They are called the ‘f-block’, for reasons we will cover in our upcoming post ‘Atomic structure and the Periodic Table’. But they don’t have to be separated from the main body of the periodic table. The periodic table is arranged in order of atomic number, so it starts with element 1, and reading left to right we go to element 2, 3, 4 etc. Now find element 57 (by the way – that’s a perfectly sensible naming scheme. We call it lanthanum, but we really could decide to call it ‘element 57’. It would be more sensible in some ways). And the next one jumps to 72!
That’s the place where the lanthanides live (see yellow arrow). Likewise, the actinides live in the space identified by the orange arrow. We only draw the lanthanides and actinides separately at the bottom because otherwise the periodic table would be unwieldy, too wide to fit comfortably on a page.
Many people know this, and yet it’s hard to remember because the periodic table is almost always drawn in the conventional manner. So here it is in all its correctly ordered glory – just because it never hurts to think about things from a different angle once in a while…
