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Elementary

My textbook lists the two-letter symbols for chemical elements, including both old and new abbreviations for some of them, as: Ac Ag Al Am Ar As At Au Ba Be Bh Bi Bk Br Ca Cd Ce Cf Cl Cm Co Cr Cs Cu Db Ds Dy Er Es Eu Fe Fm Fr Ga Gd Ge Ha He Hf Hg Ho Hs In Ir Kr La Li Lr Lu Lw Md Mg Mn Mo Mt Na Nb Nd Ne Ni No Np Os Pa Pb Pd Pm Po Pr Pt Pu Ra Rb Re Rf Rg Rh Rn Ru Sb Sc Se Sg Si Sm Sn Sr Ta Tb Tc Te Th Ti Tl Tm Xe Yb Zn Zr.

Using letters no more than once, I have written as many as possible around a circle such that, if you look at any adjacent pair of letters, then reading them clockwise they are one of the above elements. How many letters have I written?

WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 17 July. The Editor’s decision is final. Please send entries to Enigma 1754, Â鶹´«Ã½, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (please include your postal address).

Answer to 1748 Quo Vadis?: The numbers on the cards in the bottom row of the grid are 1, 3, 2 and 1.

The winner Trevor Morley of Weiterstadt, Germany