Download the structure for interactive viewingChoose one of the options below, based on which program you want to view the structure with.
For viewing with the demo version of CrystalMaker (more info)
For viewing with the commercial version of CrystalMaker (more info)Download the magnesium structure in pdb format (courtesy of WebElements.com)
For viewing with XtalDraw (more info)
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- All of the atoms have the same atomic radius. What is the coordination number of any Mg atom in this structure?
- Orient the stucture so that you are looking down the c-axis. You should see a repetition of the Mg atoms along the a-axis. What is the stacking arrangement of the layers (ABCABC, or ABAB) along the a-axis? Is this a cubic close packed (CCP) or hexagonal close packed (HCP) structure?
- Looking down on the planes of atoms you see hexagonal rings connected to form a network.
What happens if we rotate these planes? Remember to consider the atoms shown in this view as part of an infinite plane of atoms. Rotate the the structure 120°. Do similar atoms occupy exactly the same positions, or are they in a different arrangement? Try the same with a 90° and 180° rotation.The atoms repeat for 120 and 180° rotations.
It is extremely difficult to visualize the CN of Mg in this structure without the complete "ball-and-stick" rendering showing the bonds between the Mg atoms. For CrystalMaker users, perhaps the best way to answer this question is by using the "Add/Delete Bonds" tool to draw the bonds from a central Mg (within the body of the structure) to each of its nearest neighbors. Rotate the structure after adding each bond to make sure that it the the same length as the other bonds you draw.
The atoms repeat every other layer (ABAB...), so the close packing is hexagonal.