Packing in Solids

The following is a diagram of square close packed unit cell. The packing efficiency of the said solid is _____.

What is the formula of an oxide of P that crystallizes as a cubic close packed array of oxygen atoms with P atoms in two third of the octahedral holes ?

In chromium $\left(\mathrm{III}\right)$ chloride, ${\mathrm{CrCl}}_3$, chloride ions have cubic close packed arrangement and $\mathrm{Cr}\left(\mathrm{III}\right)$ ions are present in the octahedral holes. What fraction of the octahedral holes is occupied ? What fraction of total number of holes is occupied ?

What are tetrabedral and octahedral voids ? How are their radii related to the radii of the spheres in the close packed arrangement?

What is the difference between cubic close packing and hexagonal close packing? Give three examples of elements of each type. What is the coordination number in each case?

How many octahedral voids are there in $1$ mole of a compound having a cubic close-packed structure?

In a crystal of zinc sulphide, zinc occupies tetrahedral voids. What is the coordination number of zinc?

What is the coordination number of an octahedral void?

An octahedral void is _____ times than a tetrahedral void.

For two dimesional hexagonal lattice, the unit cell is _____.

In diamond lattice, all lattice points and alternate tetrahedral voids are occupied by carbon atoms. If diamond crystallizes in fcc form with edge length '$\mathrm{a}$', find out the distance between the next nearest neighbours.

In diamond lattice, all lattice points and alternate tetrahedral voids are occupied by carbon atoms. If diamond crystallizes in fcc form with edge length '$\mathrm{a}$', find out the number of next nearest neighbours in diamond lattice.

You are given marbles of diameter $10 \mathrm{mm}$. They are to be placed such that their centres are lying in a square bound by four lines each of length $40$. What will be the arrangement of marbles in a plane so that maximum number of marbles can be placed inside the area? Sketch the diagram and derive an expression for the number of marbles per unit area.

If silver iodide crystallizes in a zinc blende structure with ${\mathrm{I}}^{-}$ ions forming the lattice, then calculate fraction of the tetrahedral voids occupied by ${\mathrm{Ag}}^{+}$ ions.

The mineral haematite, ${\mathrm{Fe}}_2{\mathrm{O}}_3$ consists of a cubic close packed array of oxide ions with ${\mathrm{Fe}}^{3+}$ ions occupying interstitial positions. Predict whether the iron ions are in the octahedral or tetrahedral holes. Radius of ${\mathrm{Fe}}^{3+}=0·65 \mathrm{Å}$ and that of ${\mathrm{O}}^{2-}=1·45 \mathrm{Å}$.

Briefly explain how the packing of the constituent particles in a crystal takes place.

In a compound, atoms of elements $\mathrm{Y}$ form ccp lattice and those of element $\mathrm{X}$ occpy $\raisebox{1ex}{$2$}\!\left/ \!\raisebox{-1ex}{$3$}\right.\mathrm{rd}$ of tetrahedral voids. The formula of the compound will be 

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

What is the formula of a compound in which the element $\mathrm{Y}$ forms ccp lattice and atoms $\mathrm{X}$ occupy $\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.$rd of tetrahedral voids.

Describe briefly about three dimensional close packing from two dimensional square close-packing.