An Easily Constructed Tetragonal Pyramid Model Shukichi Yamana Faculty of General Education. Kinki University. Kowskae. Higashi Osaka 577.
Japan
Amodelof a tetragonal pyramid, which is useful for teaching stereochemistry (for example of pentahorane, BsHs)' can be made easily by using a sealed, empty envelope. The steps (illustrated in the figure) are given below. (1) The first figure shows the starting configuration,which is pro-
duced by steps 1-6 of the previous a~ticle.~ But here, the horizontal line perpendicular to the left-hand side of the envelope atFcrosses theline (C) and the right-handside ofthe envelope at G and H, respectively.
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Journal of Chemical Education
(2) The left lower part of the envelope is folded up at Fso that the corner A falls on the line (D). That point is marked I. (3) The left lower part of the envelope is unfolded. (4) A horizontal line perpendicular to the line (D) at I is drawn so
that it crosses the left- and right-hand sides of the envelope and the line (E)at J,L, and K, respectively.
' Dulmage, W. J.: Llpscomb, W. N. Acta Cryst. 1952, 5, 260. Yamana, S. J. Chem. Educ. 1988,65,1071.
( 5 ) On the reverse of the envelope, the points corresponding to I ,
K, and G are marked I*, K*, and G*, respectively. (6) Four squares (FACG and GCBH on the front and HBCG* and GXCAFonthe hack) are marked a,, az, 0 3 , and ad, respectively. (7) The lower part of the envelope is cut along the line CG (i.e., CG*) and the point C i s rewritten as CI and C,, respectively, accordingto the sideson which they aresituated ( I = left, and r =right). (8)The lower part of the envelope is cut along the lines of CIA,AF, C,B, and BH. The points A, Ci, C,, and B are rewritten as (,A and aA), (&i and &I): (4,and aC,), and (,Band A,respectively, according to the s ~ d e on s which they are situated V = front; and b =back). (9) The upper part of the envelope is cut off along the line JL. (10) Ohliquelinesaredrawn to shade the four triangles (IGKon the front;I*G*K* on the back; andHKH* andIFI* on both sides).
(11) The remaining portion is folded both backward and forward along the lines FG (i.e., FG*), GH (is., G*W, FI (i.e., FZ*), ZG (i.e., Z*G*), GK (i.e., G*K*), K H (i.e., K*W and (C). (12) The right- and left-hand sides of the envelope are pushed toward each other so that four lines (FG, GH, HG", and G*F) form four sides of a square. (13) Faces marked with the letter a are brought together and stacked in the order given by their numerals to produce a base of the modelgiven in the title. Thus, four faces ol,oz, as, a n d a l are piled on each other in numerical order so that the face having the largest numeral, a4, is outside and the others 0 1 - 0 3 are folded inside. The sides of this base are taped. (14) Four points I , K, K*, and I* are pushed together and the four shaded creased triangles (ZGK,KHK*, K*G*I*, and I*FO are folded inside. The sides are taped together to produce the model desired.
Volume 65
Number 12
December 1968
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