The common structures having cn = 4 for transition- metal complexes are tetrahedral and square planar. however, these are not the only conceivable structures. examples of main group compounds having seesaw structures are known, and trigonal-pyramidal structures may also be possible in some cases.

28. which is not a reason that water is used to store spent fuel rods from nuclear power plants? water increases the speed of the chain reaction in the fuel rods. water protects nuclear power plant workers from the high temperature and radiation of the fuel rods. water acts as a radiation shield to reduce the radiation levels. water cools the spent rods. salts action