Page "learned" Paragraph 47

If the Af bond is linear then there are three reasonable positions for the hydrogen atoms: ( 1 ) The hydrogen atoms are centered and hence all lie on a sheet midway between the oxygen sheets ; ;

( 2 ) all hydrogen atoms lie on a sheet, but the sheet is closer to one oxygen sheet than to the other ; ;

( 3 ) hydrogen atoms are asymmetrically placed, either randomly or in an ordered way, so that some hydrogen atoms are closer to the upper oxygen atoms while others are closer to the lower oxygen atoms.

Position ( 2 ) appears to us to be unlikely in view of the absence of a piezoelectric effect and on general chemical structural grounds.

A randomization of `` ups '' and `` downs '' is more likely than ordered `` ups '' and `` downs '' in position ( 3 ) since the hydrogen atoms are well separated and so the position of one could hardly affect the position of another, and also since ordered `` up '' and `` down '' implies a larger unit cell, for which no evidence exists.

Therefore, the only unknown structural feature would appear to be whether the hydrogen atoms are located symmetrically ( 1 ) or asymmetrically ( 3 ).