Why in periodic table normally we have elements with FCC and HCP structure?

[swapneel5]

what is basic principle followed by atoms to arrange in basic structure?

 

[Useful nucleus]

Minimizing the energy as much as possible! Close packing as in HCP and FCC seems to do the job very well. However, for some elements due to subtle electronic structure details, minimizing the energy stablizes BCC and in one case (alpha polonium) stablizes the simple cubic structure.