In the past somebody showed me the puzzle below. I remember the answer but not the entire solution. Here it goes:

On a grid of 2x2 put four single letter chemical elements. The result should have two letter elements on the horizontal, vertical and diagonal.

  • 1
    $\begingroup$ So, what exactly is the question?? $\endgroup$ – Sid Aug 3 '16 at 15:34
  • $\begingroup$ Well I thought there should be a element in every direction. So ltr and rtl. By now I know that's impossible. What frustrated me is that there are two possibilities depending on the direction you read the diagonal. $\endgroup$ – Peter Janssen Aug 3 '16 at 16:17

The answer is:

First row:


Second row:


The elements are:

Sn - Tin, Bi - Bismuth, Sb - Antimony, Ni - Nickel, Si - Silicon, Nb - Niobium

  • $\begingroup$ I've just deleted my comment cause you spotted the diagonals :) $\endgroup$ – rhsquared Aug 3 '16 at 15:38
  • $\begingroup$ +1 I saw the answer for the diagonal from upper left to lower right, but did not consider the one from lower left to upper right. $\endgroup$ – Herb Wolfe Aug 3 '16 at 15:40
  • $\begingroup$ How is this not accepted and the other, later one is accepted? $\endgroup$ – EKons Aug 3 '16 at 19:01
  • $\begingroup$ @ΈρικΚωνσταντόπουλος both answers are correct if you reverse the reading direction of the diagonal. To me left-to-right seems more logical than top-to-bottem. Although 11 people disagree. Is there a rule of thumb when reading diagonally? I can't find anything about it on the web. $\endgroup$ – Peter Janssen Aug 3 '16 at 20:12

Taking a quick look at a period chart, the only valid answer, giving your hint is:



Antimony (Sb)
Tin (Sn)
Silicon (Si) Nickel (Ni)
Bismuth (Bi)

  • $\begingroup$ @PeterJanssen There is no element with the symbol Bn $\endgroup$ – GoodDeeds Aug 3 '16 at 15:49
  • $\begingroup$ It seems that there is consensus about what direction a diagonal needs to be read. $\endgroup$ – Peter Janssen Aug 3 '16 at 16:19
  • 3
    $\begingroup$ Nb is niobium, which isn't explicitly listed in the elements above. $\endgroup$ – Michael Seifert Aug 3 '16 at 18:59
  • $\begingroup$ How do you know this is the only answer? (The search space is pretty small, so I suppose exhaustive search would be trivial) $\endgroup$ – Alexander Aug 3 '16 at 22:47
  • $\begingroup$ The original question had the letters I, s, b, and n in the hint. $\endgroup$ – Herb Wolfe Aug 3 '16 at 23:27


S: Sulfur
Si: Silicon
Sb: Antimony
Sn: Tin
I: Iodine
In: Indium
N: Nitrogen
Ni: Nickel
Nb: Niobium
B: Boron
Bi: Bismuth


Row entries: 2
Column entries: 2
Total entries: 4
Additional entries: 11
Other entries: [CHEM_EL] 11 [CHEM_EL_L2] 7
Total: 15
Other tallies: [DUPE] 0


First row:


Second row:


And the elements are:

Scandium (Sc), Cesium (Cs), Nobelium (No), Tin (Sn), Cobalt (Co), Copernicium (CN -diagonal), Osmium (Os - diagonal)

  • $\begingroup$ Kudos for using Cn. Wasn't named when I first heard about this puzzle. $\endgroup$ – Peter Janssen Aug 4 '16 at 19:11

My answer is

Sc and In
Sc=Scandium, S=Sulfur, C=Carbon
In=Indium, I=Iodine, N=Nitrogen

  • 4
    $\begingroup$ Neither Ci nor Ic is a chemical element $\endgroup$ – Peter Janssen Aug 3 '16 at 17:18
  • $\begingroup$ Welcome to Puzzling.SE! Please double-check the question contents and your answer to see if it is correct. Here, the elements Ci and Ic are specified, but they do not exist. $\endgroup$ – EKons Aug 3 '16 at 19:03

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