Crystal systems in which no two axial lengths equal are

Given is the arrangement of atoms in a crystallographic plane. Which plane correctly represent(s) the drawn structure?

Which mineral can have the silicates skeleton as shown below?

Copper has a face-centred cubic structure with a unit-cell edge length of $3.61 \mathrm{\AA }$. What is the size of the largest atom (in pm), which could fit into the interstices of the copper lattice without distorting it?

[Hint: Calculate the radius of the smallest circle in the figure.]

A metal cystallises into two cubic phases, f.c.c and b.c.c. whose unit-cell lengths are $3.5 {\mathrm{A}}^{°}$ and $3.0 \mathrm{A}°$. Calculate the ratio of densities of f.c.c. and b.c.c.

Give answer after multiplying with 100 and rounding off to the nearest integer value.

Potassium metal crystallizes in a face-centred arrangement of atoms where the edge of the unit cell is $0.574 \mathrm{nm}$. Determine the shortest separation of any two potassium nuclei in pm is.