Between square and hexagonal close packing in two dimensions, which one represents the most effective packing, and why?

How many types of close-packing are possible when identical spheres pack together in a plane? Which one of these represents the highest efficiency in close-packing in two dimensions? Mention coordination number in each of these close-packing.

In which pair most efficient packing is present-

Packing refers to the arrangement of constituent units in such a way that the forces of attraction among the constituent particles is the maximum and the contituents occupy the maximum available space. In two dimensions, there are hexagonal close packing and cubic close packing. In three dimentions, there are hexagonal, cubic as well as body centred close packings. The empty space left in ccp packing is:

Packing refers to the arrangement of constituent units in such a way that the forces of attraction among the constituent particles is the maximum and the contituents occupy the maximum available space. In two dimensions, there are hexagonal close packing and cubic close packing. In three dimentions, there are hexagonal, cubic as well as body centred close packings. The space occupied by spheres in bcc arrangement is:

Packing refers to the arrangement of constituent units in such a way that the forces of attraction among the constituent particles is the maximum and the contituents occupy the maximum available space. In two dimensions, there are hexagonal close packing and cubic close packing. In three dimentions, there are hexagonal, cubic as well as body centred close packings. The pattern of successive layers in ccp arrangement is:

Packing refers to the arrangement of constituent units in such a way that the forces of attraction among the constituent particles is the maximum and the contituents occupy the maximum available space. In two dimensions, there are hexagonal close packing and cubic close packing. In three dimentions, there are hexagonal, cubic as well as body centred close packings. A certain oxide of a metal M crystallises in such a way that O^(2-) ions occupy hcp arrangement following ABAB... pattern. The metal ions however occupy 2//3 rd of the octahedral voids. The formula of the compound is :

In two dimensions, which one represents the close-packed structure of spheres with highest packing efficiency, a square close-packing or a hexagonal close-packing? Explain in it terms of coordination number of sphere in each case.

In sapphire, oxide ions are arranged in hexagonal close packing and aluminium ions occupy two-thirds of the octahedral voids. What is the formula of sapphire?

Mention the name and the position of two elements, one of which is most electronegative annd other is most electropositive in periodic table.

Assertion: Hexagonal close packing in more light than cubic close packing. Reason: Hexagonal close packing has C.N of 12 whereas cubic close packing has C.N. of 8.