Coordination Number

Q. HEXAGONAL CLOSE PACKING(HCP) HAS TETRAHEDRAL AS WELL AS OCTAHEDRAL VOIDS. THE TOTAL NO OF OCTAHEDRAL AND TETRAHEDRAL VOIDS PER UNIT CELL ARE 6 AND 12 RESPECTIVELY. THE NO OF TETRAHEDRAL VOIDS COMPLETELY INSIDE THE UNIT CELL(DO NOT HAVE CONTRIBUTION IN ANOTHER UNIT CELL) IS X.THE VALUE OF 2X IS

Q. In Calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion $\left(C{a}^{2+}\right)$ and fluoride ion $\left(F^{-}\right)$ are

1. 8 and 4
2. 6 and 6
3. 4 and 2
4. 4 and 8

Q.

What is the coordination number of sodium in Na2O

Q. Titanium crystallizes in a face centred cubic lattice. It reacts with carbon or hydrogen interstitially by allowing atoms of these elements to occupy holes in the host lattice. Hydrogen occupies tetrahedral holes but carbon occupies octahedral holes the formula of titanium carbide and hydride are

Q.

What is the two dimensional coordination number of a molecule in square close packed layer?

Q.

A cube solid is made up of two elements P and Q. Atoms of Q are at the corners of the cube and P at the body - centre. What is the formula of the compound ? What are the coordination numbers of P and Q ?

Q.

The radius of Na⁺ ion is 95pm and that of Cl^- ion is 181pm. Predict whether the coordination number of Na⁺ ion is 6 or 4 ?

Q. A compound contains two types of atoms X and Y. It crystallizes in a cubic lattice with atoms X at the corners of the unit cell and atoms Y at the body centre. The simplest possible formula of this compound is

1. $XY$
2. $X_{8}Y$
3. $X_{2}Y$
4. $X{Y}_8$

Q. An element crystallises in a structure having F.C.C unit cell of an edge 200 pm, 200 gm of it contains 24 $\times {10}^{23}$ atoms. What is the density?

1. $41.6gm/c{m}^3$
2. $42.6gm/c{m}^3$
3. $43.6gm/c{m}^3$
4. $44.6gm/c{m}^3$

Q. $CsCl$ crystals are formed by bcc crystal lattice where $C{l}^{-}$ occupies the corners and $C{s}^{+}$ occupies the centre of the cube.

The density of crystalline $CsCl$ is $4g/cc$. The effective volume occupied by a single $CsCl$ ion pair in the crystal is
[Molar mass of $CsCl=168gmo{l}^{-1}$

1. $7\times {10}^{-23}cc$
2. $14\times {10}^{-22}cc$
3. $5\times {10}^{-23}cc$
4. $12\times {10}^{-23}cc$

Q. A certain solid has a structure in which $X$ atoms are located at the corners of the cubic cell, $O$ at the edge centres and $Y$ at the body centres. Then the formula of the cell is $X_a{Y}_b{O}_c$.
If $O$ atoms are missing from any two edge centres per unit cell, the formula is $X_x{Y}_y{O}_z$.
Find the value of $(a+b+c)+(x+y+z)$.

Q.

What is meant by the term 'coordination number ?

What is the coordination number of atoms

(a) in a cubic close - packed structure ?

(b) in a body - centred cubic structure ?

Q. Why is geometrical isomerism not possible in tetrahedral complexes, having two different types of unidentate ligands coordinated with the central metal ion?

Q. What is the co-ordination number of Mn in [Mn_{​​​​​2}(CO)₁₀]?How.

Q.

AB is an ionic solid.if the ratio of ionic radii of A+ and B- is 0.52 .what is the coordination number of B-?

Q. A metallic element has a cubic lattice. Each edge of the unit cell is $2A^{\circ }$. The density of the metal is 2.5g/$c{m}^3$. The unit cells in 200 g of metal are

1. ${10}^{22}$
2. ${10}^{24}$
3. ${10}^{20}$
4. ${10}^{25}$

Q. If the coordination ofCa²⁺inCaF² is 8, then the coordination number of F^- ion would be

1. 3

2. 4

3. 6

4. 8

Q.

Two ions $A^{+}$ and $B^{-}$ have radii 88pm and 200pm, respectively. In the close-packed crystal of the compound AB, predict the coordination number of $A^{+}$

1. 5

2. 4

3. 6

4. 7

Q. Number of parameters required to define a 1-D space lattice is

1. 1
2. 3
3. 6
4. 2

Q.
In the given sphere, the black spheres forms the first layer and red sphere forms the second layer and blue sphere forms the third layer.
The correct representation of the given arrangement of spheres is

1. Hexagonal close packing
2. Cubic close packing
3. bcc close packing
4. Square close packing

Q. In a face centered cubic unit cell, the ratio of number of alternate tetrahedral voids to the lattice points is

Q.

Potassium crystallizes in a bcc lattice, hence the coordination number of potassium in potassium metal is

[KCEE 1993]

1. 6

2. 8

3. 0

4. 4

Q. Silver crystallises in a face-centred cubic unit cell. The density of $Ag$ is $10.5gc{m}^{-3}$. Calculate the volume of unit cell (in $c{m}^3$).

1. $68.3\times {10}^{-24}c{m}^3$
2. $24.2\times {10}^{-24}c{m}^3$
3. $14.8\times {10}^{-26}c{m}^3$
4. $77.4\times {10}^{-28}c{m}^3$

Q. An element 'X' (At. mass = 40 g $mo{l}^{-1}$) having FCC structure, has unit cell edge length of 400 pm. Calculate the density of 'X' and the number of unit cells in 4 g of 'X'.

$(N_A=6.022\times {10}^{23}mo{l}^{-1})$

Q.

Body centered cubic lattice has a coordination number of

[AIIMS 1996; MP PMT 2002]

1. 8

2. 12

3. 6

4. 4

Q. Element 'B' forms a CCP structure, and 'A' occupies half of the octahedral voids, while oxygen atoms occupy all the tetrahedral voids. Structure of the bimetallic oxide is:

1. $A_{2}B{O}_4$
2. $A{B}_2{O}_4$
3. $A_2{B}_{2}O$
4. $A_4{B}_{2}O$

Q.

If the radius of Mg2+ ion, Cs+ ion, O2- ion, S2- ion and Cl- ion are 0.65 Å , 1.69 Å, 1.40 Å, 1.84 Å, and 1.81 Å respectively. Then the co-ordination numbers of the cations in the crystals of MgS, MgO and CsCl respectively are:

1. 6, 4, 8

2. 4, 6, 8

3. 1, 2, 4

4. 2, 1, 4

Q. Consider an atom (B) lying in the square planar void created by atoms of A. The radius of B is $r_B.$ In another lattice, atom (C) lies in the octahedral void created by atoms of A and the radius of atom $C$ is $r_C.$ Assuming both these crystals to be ideal, the correct statement is

1. $r_B=2r_c$
2. $r_e=r_c$
3. Information insufficient
4. $r_B<r_c$

Q. The coordination number of a metal crystallizing in a hexagonal close-packed structure is

1. 4
2. 12
3. 6
4. 8

Q. For some crystals, the radius ratio for cation and anion is 0.525, its coordination number will be

1. 4

2. 2

3. 6

4. 8