Silicon, germanium and grey tin (all with the same structure as diamond) are also brittle solids. Once you apply enough energy to break the existing carbon-carbon bonds, that's it! However, if you hit it with a hammer, it shatters. There is a much clearer non-metal / metal difference shown if you look at the brittleness of the elements.Ĭarbon as diamond is, of course, very hard - reflecting the strength of the covalent bonds. I have to admit to choosing this set because it shows simple, largely unbroken patterns! There is an awful lot of variability in the data depending on where you get it from. Note: The data in this chart comes from the University of Sheffield's excellent Webelements site. The tin values in the chart refer to metallic white tin. 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 trends reflect the increasing weakness of the covalent or metallic bonds as the atoms get bigger and the bonds get longer. 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. There is therefore a clear trend from the typical covalency found in non-metals to the metallic bonding in metals, with the change-over obvious in the two entirely different structures found in tin. Use the BACK button on your browser to return to this page. The first link will actually lead you to the second one if you want to explore both of these topics. Note: If you aren't sure about metallic bonding or metallic structures, you should follow these links before you go any further. In close-packing, each atom is surrounded by 12 near-neighbours.īy the time you get to lead, the atoms are arranged in a straightforward 12-co-ordinated metallic structure. The structure is a distorted close-packed arrangement. The common allotrope of tin ("white tin" or "beta-tin") is metallic and has its atoms held together by metallic bonds. The diagram shows a small part of that structure.Įxactly this same structure is found in silicon and germanium and in one of the allotropes of tin - "grey tin" or "alpha-tin". Use the BACK button on your browser to return quickly to this page.ĭiamond has a three-dimensional structure of carbon atoms each joined covalently to 4 other atoms.
It would probably be worth your while to read this page before you go any further. The structures of diamond and graphite are explored in more detail on a page about giant covalent structures in another part of this site.
The trend from non-metal to metal as you go down the Group is clearly seen in the structures of the elements themselves.Ĭarbon at the top of the Group has giant covalent structures in its two most familiar allotropes - diamond and graphite.Īllotropes: Two or more forms of the same element in the same physical state. It describes how this trend is shown in the structures and physical properties of the elements, and finally makes a not entirely successful attempt to explain the trend. This page explores the trend from non-metallic to metallic behaviour in the Group 4 elements - carbon (C), silicon (Si), germanium (Ge), tin (Sn) and lead (Pb). THE TREND FROM NON-METAL TO METAL IN THE GROUP 4 ELEMENTS The trend from non-metal to metal in Group 4