important Question *

[1] Why crystalline solid is called real solid?

Answer:- (1) A crystalline solid is called a real solid because its constituent particles are arranged in a definite geometry.

*Q – 2 What is the difference between crystalline and amorphous solids?

crystalline

amorphous

2 – The melting point of this is fixed

3 – These are called real solids

4 – It shows anomalous countryside

5 – Their cooling curve is continuous

Ex-diamond

The melting point of 2- in is not fixed

3- These are also called virtual solids

4- It shows even decency

Ex-glass

(a) vacuole defect (b) interstitial defect

(a) Vacancy defect

The defect in which some particles leave their fixed position and move out of the crystal lattice is called Vacancy defect
Note- Due to this defect the density of crystal decreases.
This defect increases with increase in temperature.
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(b) Interspace defect

The defect in which some extra particles get into the inner space of the crystal lattice is called interspace defect.

(a) – due to presence of intra-cosmic excess positive charge (b) – due to anionic vacancy defect

(A) due to presence of intra-cosmic excess positive charge

In this type of defect some extra fuel enters the space of the ionic crystal lattice, electrons also come into the other space to maintain the neutrality of the crystal
Due to the presence of unpaired electrons in this type of defect crystals, the magnetically colored conductors are
This defect occurs when ZnO is heated, due to which its color becomes yellow.

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(B) Anion Vacancy Defect

In this type of defect, some negative ions leave their fixed position and move out of the crystal lattice, their place is taken by the electron, due to which the electrical neutrality of the crystal remains. The location is called the color center or the color of the crystal becomes darker as the number of F centers increases.

Thus colourless, non-magnetic, conductors are
For example, yellow color of a- Nacl crystal- its yellow color crystal has electrons instead of Cl(-), due to which its color is yellow.
b- Similarly the color of Kcl is purple and the color of Licl is pink

Note :- If a crystal of NaCl is heated with the vapor of Na atom then the vapor of Na atom spreads on the surface of the crystal and Cl- gets distributed on the surface of the crystal and NaCl reacts with Na+ ions on the surface. makes up
The electron lost during the formation of Na+ from Na+ goes along with Cl- and imparts yellow color to the crystal.

Impurity or impurity defect

Addition of other ionic impurities to the ionic compound increases their conductivity, this process is called doping or doping.
For example, by melting a crystal of NaCl, it crystallizes by adding a small amount of Srcl impurity.

Due to which Sr+2 ion comes in place of Na+ ion somewhere in the crystal because the oxidation state of Sr is +2, so for one Sr+2 ion, 2Na+ ions vacate their place where Sr+2 comes. and a space is left vacant, due to this vacancy, conductivity arises in the crystal.

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Crystal lattice or three dimensional lattice

The regular arrangement of the constituent particles in a crystalline solid is called stereoscopic lattice or crystal lattice.

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The smallest unit of the whole crystalline number whose repeating the same number of times in all directions reproduces the crystal structure is called unit cell.

Characteristics of a unit cell

(1) The three dimensions of a unit cell are shown by a, b, c, this param may or may not be perpendicular to each other.

(2) The angles between the three angles of a unit cell are represented by alpha, beta, gamma.
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Hence, a unit cell is represented by 6 parameters a,b,c,alpha,beta,gamma

Types of Unit Cells

It is divided into two parts
(1) primitive or simple unit cell (2) centered unit cell

(1) Primal or Simple Unit Cell

The unit cell in which the constituent particles are located at the corners is called primitive or simple unit cell.

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In this, 8 constituent particles are present at 8 angles of the unit cell and the contribution of each particle is (1 x 8) for one of its cells.
So total number of constituent particles = 8×[1/8】= 1 particle

(2) Centered Unit Cell

The unit cell in which the constituent particles are present at positions other than the corners is called concentrated unit cell.
It is divided into three parts.

(1) Intracentred/Body Centered Unit Cell (BCC)
(2) Face Centered Unit Cell (FCC)
(3) End Centered Unit Cell (ECC)

(1) Intracentred/Body Centered Unit Cell (BCC)

The unit cell in which the constituent particles are located at the center other than the corners is called intermolecular unit cell.

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In this, 8 constituent particles are present at the 8 corners of the unit cell, whose contribution is 8×[⅛]=1 and the contribution of the particle at the center is 1, so the total number of constituent particles in the unit cell is 2.

(2) Face Centered Unit Cell (FCC)

The unit cell in which the constituent particles are located at the center of each face except at the corners is called face centered unit cell.

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In this, eight particles are present at the eight corners of the unit cell, whose contribution is 8×(⅛) = 1 and the contribution of the particles located at the center of all the 6 faces is 6×(1/2/) =3
Hence, the total number of constituent particles in the unit cell is 4.

(3) End-centered unit cell (ECC)

The unit cell in which the constituent particles are located on any two opposite faces other than the corners is called end-centered unit cell.

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In this, 8 constituent particles are present at 8 corners of the unit cell, the contribution of the day is 8×[⅛] =1 and the contribution of the angles at the center of the two opposite faces is 2×(1/2) =1 so the unit cell is The total number of constituent particles in

In this type of seamless packaging the constituent particles (sphere) are arranged in a line in such a way that one sphere touches the other two adjacent spheres, hence the packaging capacity of this smooth packaging is 2.

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Two dimensional unidirectional packaging is divided into two parts
(1) square – seamless packaging
(2) hexagonal smooth packing

(1) Square-Nibid packaging

In this type of seamless packaging, the second row is placed on the first row in such a way that the shells of the second row are located immediately above the circles of the first row, similarly other rows are kept.

If the first row is called A, then the second, third and other rows will also be called A.
So AAAA…….. some sort of arrangement is obtained
In this arrangement, each sphere touches four adjacent spheres whose centers are joined to form a square, hence it is called a square-neighboring complex.
The coordination number of this smooth packaging is 4.

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(2) Hexagonal Nimble Compression

In this type of smooth packaging, the second row is arranged on the first row in such a way that the shells of the second row come in the depression (trough) made of the first row’s balls, in this case the shells of both the rows do not lie in a line
If the arrangement of the first row is called A, then the arrangement of the second row is called B.
The third row is called A because of its similarity to the first row, thus the arrangement of ABABAB….. is obtained.

In the same arrangement, a sphere touches other 6 adjacent spheres whose centers are joined to form a hexagon. The coordination number of such a smooth clustering is 6.

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This type of smooth packaging is obtained as follows
(1) – Two-dimensional square, three-dimensional, non-contiguous packaging of layers: – In this type of non-uniform packaging, the second layer is placed on the first layer in such a way that the shells of the second layer are located just above the first layer, in this way the other layers also are kept
If the first layer is called A, then the second layer will also be called A.
So AAAAAA…… type of arrangement is obtained.

The lattice thus obtained is called simple cubic lattice and its unit cell is called simple cubic unit cell.

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(2) Two-dimensional Hexagonal Nimble Packed Layers with Three Dimensional Nimble Complexes

In this nimble packaging the layers can be arranged in the following way

(1) Laying the second layer on the first layer

The second layer is placed on the first layer in such a way that the shells of the second layer are placed on the sphere of the first layer in such a way that the shells of the second layer are formed by the depression of the shells of the first layer. get into the trough
In this case, the spheres of the two layers are not on the same line.

Therefore, if the arrangement of the properties of the first layer is called A, then the arrangement of the spheres of the second layer is called B.
In this arrangement tetrahedral spacing (hole) as well as octahedral spacing are obtained.

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(A) Laying the third layer on the second layer

They are kept in two ways

(1) – Covering of tetrahedral voids

The third layer is placed on the second layer in such a way that the spheres of the third layer lie just above the tetrahedral voids, in this case the arrangement of the spheres of the third layer is the same as that of the first layer, hence the third layer will be called A, in this way, these layers are repeated in an alternate order, which gives ABABAB… is 74%
e.g. mg and zn

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The third layer is placed on the second layer in such a way that the shells of the third layer completely cover the octahedral voids of the second layer
In this situation, the third layer, the second layer, the spheres of the first layer are not in a line, that is, the arrangement of the three layers is different, so if the arrangement of the spheres of the third layer is called C, then the structure of ABCABCABC… would be obtained. This structure is called Cubic Nict Balanced Structure (ccp) or Face Centered Nict Complex Structure (fcc).

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With the help of dimensions, the relation between unit cell volume, atomic mass, density of unit cell, and Avogadro numbers is established.

If the length of the sides of the unit cell is A and the volume of the unit cell is a³.
Mass of unit cell = Number of atoms present in unit cell (n) × Mass of one atom (m)

Therefore, density of unit cell (d) = [mass of unit cell] [volume of unit cell]

d = (n×m)÷ a³

Mass of an atom(m) = M(molar mass) (Na Avogadro number)

d = (n×m) (a³ ×Na)

Note: – The density of the unit cell is the density of the substance, and the density is expressed in gm/cm.

Packing capacity (P. E)

The amount of volume that the constituent particles present in the crystal lattice occupies the crystal lattice is called its packing capacity (efficiency).
Therefore

Packaging capacity = (volume of sphere present in crystal lattice) (total volume of crystal lattice)

Percentage packing capacity = (volume of spheres present in crystal lattice) ×(100) (total volume of crystal lattice)

Packaging capacity of dense nibid packed structure o

(1) – Simple cubic nibid complex structure – In this structure the spheres (particles) are located at the corners of the cube and the spheres at the corners touch each other

(2) Intracenter/Body Centered Unit Cell (BCC) :- As shown in the photo below

(3) Face Centered Unit Cell (FCC) :- As shown in the photo below

>All electrons are in paired state
The effect of magnetic moment produced by one electron is canceled by the magnetic moment produced by another oppositely spinning electron, this property of solids is called Precious Magnetism.
Ex – Na+, Zn+, Nacl, Zno, H- etc..

(2) – Paramagnetic solids

Such solids which are weakly attracted when placed in an external magnetic field are called paramagnetic solids.
Unpaired electrons are present in this, so they are attracted to the magnetic field, as long as they are present in the magnetic field, they act like a magnet and they lose their magnetism when the magnetic field is removed, this property of solids is called paramagnetism. Permanent magnets are made from materials
Eg – Cuo, Tio, Cu+² etc..

(3) – Iron magnetic solid (Ferro magnetic solid)

Such solids which are strongly attracted when placed in an external magnetic field are called iron magnetic solids.
In the solid state, the metal ions of iron-magnetic materials are grouped into small blocks called domains. Each domain behaves like a small magnet. In the absence of a magnetic field, the domains are disordered, and hence, the effects of each other are limited. They cancel each other out whereas in the presence of a magnetic field all the domains automatically orient in one direction and produce a strong magnetic effect, they exhibit magnetic properties even after the magnetic field is removed, so permanent magnets are made from these solids. property iron is called magnetism
Eg – Fe, Co, Ni

(4) – Small iron magnetic solids

The structure of these solids is similar to that of iron magnetic solids, but the orientation of the domains is opposite and unequal to each other, so this property of solids is called small iron magnetism. Huh
For example – Hematite (Fe2 O3) and Magnetite (Gee O4)

(5) – Anti-iron magnetic solid (Anitfero)

The structure of these solids is also similar to that of iron magnetic solids, but the magnetic moment of the domains is opposite to each other, so they cancel the effect of each other. property of love iron is called magnetism
Eg – Mno2, Mn2 O3, Cr2 O3

According to the band theory, when the atomic orbitals overlap each other to form molecular orbitals, a band-like structure is obtained due to the very small energy gap between these orbitals, hence the name of band theory. is known from
On the basis of band theory, types of conductors, insulators and semiconductors are defined.

(1) – Conductors

In conductors (metals) either the valence band is partially filled or the valence band overlaps between the next vacant conduction band, so electrons move from the valence band to the conduction band after getting some energy. and displays conductivity

(2) – Insulators

In non-metals, the valence band is completely filled but due to the large energy gap between the fully filled valence band and the next vacant conduction band, the electron does not gain energy from the valence band to the next conduction band. hence they do not show conductivity

(3) Semiconductors

In semiconductors the valence band is completely filled and the energy gap between the valence band and the next vacant conduction band is very small, so electrons move from the valence band to the conduction band after getting little energy and the low conductivity show

Note – The conductivity of semiconductor increases with increase in temperature because the number of electrons moving from valence band to vacant conduction band increases with increase in temperature.