### Periodic puzzle

 I'm drinking my coffee from this mug today
Last night's episode of Endeavour, the prequel to Inspector Morse, in which we see a young Detective Constable Morse learning his trade, featured one of those fiendishly complex puzzle-based clues that I am sure real-world detectives never come across (but are still fun for the viewer).

Morse spotted that the set of hymn numbers on a hymn board in a church (which we had earlier seen the soon-to-be-murdered vicar putting up) were strange. The numbers were 74, 17, 18, 19. I was slightly pleased with myself to spot that this was an unusual collection of numbers and probably meant something, but kicked myself for not spotting the clues the writer had carefully provided us for doing the decoding.

We knew that the vicar loved puzzles, had been a cryptographer during the war, and previously had been a chemist - there was even a framed periodic table on the wall of his house.

What Morse spotted, but I kicked myself for not doing, was that if you write out the chemical symbols of the elements with the atomic numbers the vicar put up on the board you get:

W ClArK

And low and behold, the murderer was one W. Clark Esq. Clever, eh?

What struck me since is that I could not do the same for myself. I could do a rather mangled B ClErGe, which might give you a clue, but without an E or a G, it's a bit of a mess. And that led me on to wonder just what the people who devised the chemical symbols were smoking (or inhaling in their fume cupboards).

It all starts well with a simple rule that seems to be 'use a single letter for the first instance and a two letter variant for subsequent ones.' So in the first couple of rows of the table we get the single letters H, B, C, N, O and F, with He and Be for the next instances. But why is lithium, the first L, Li instead of L? Why is magnesium, the first M, Mg instead of M? You might assume that they decided not to use any more single letter names. Only we later come across P, S, K, V, Y, I (not even the first I) and W.

It's totally bonkers.

1. Brian, you really should get out more.

2. Well, wouldn't it make sense that shorter single-character abbreviations were given to more abundant, common elements that were discovered earlier, and most of the more complex names have been given to rarer elements that have been discovered later?

I suppose Mendeleyev and other similar pioneers had a big say on how the elements were named and abbreviated.

3. Yes it would make sense - but it doesn't explain why there is, for example, Mg but not M. I don't think it was down to Mendeleev, I think it was mostly Berzelius, but what I don't understand is why he wasted all those handy single letters!

4. My guess is that M was used for some other element, perhaps based on a name in some particular language, but that name for the element is not well known so some other name and abbreviation was then picked up.

Many of the elements as well as names have been discovered and decided independently, at roughly the same time but in different places. At those times, it took perhaps years for news about such a discovery in physics to travel across the known world (let's say, from Russia to Prussia to France to Britain, etc).