why their is non uniformity in the periodic trends in the groups like in group 4 it is expected that the melting point of tin(Sn) is greater than lead(Pb) but infact it is lower than lead.
Plz Help

Question

why their is non uniformity in the periodic trends in the groups like in group 4 it is expected that the melting point of tin(Sn) is greater than lead(Pb) but infact it is lower than lead.
Plz Help

australopithecus · Answer

Melting points and boiling points If you look at the trends in melting and boiling points as you go down Group 4, it is very difficult to make any sensible comments about the shift from covalent to metallic bonding. The trends reflect the increasing weakness of the covalent or metallic bonds as the atoms get bigger and the bonds get longer. "The low value for tin's melting point compared with lead is presumably due to tin forming a distorted 12-co-ordinated structure rather than a pure one. The tin values in the chart refer to metallic white tin." source: http://www.chemguide.co.uk/inorganic/group4/properties.html Essentially they are saying that it is due to tin favoring a specific allotrope that makes it melt at a lower temperature. I'm sure there is a reason for this you can probably search to find a better explanation if you are interested further just look up allotropes of tin.

anonymous · Answer

thanx