Solid State of Chemistry
1. Why are solids rigid?
Solids are rigid because of the relative stronger intermolecular attractions between
them as compared to solids and liquids. Those all forces are electrostatic in nature.
The molecules which are packed together. It retains its shape and density when not
confined. The atoms or molecules of matter in the solid state are generally
compressed as tightly due to their repulsive forces among them .
2. Why do solids have definite volume?
(a) Solids have definite shape and definite volume because the
molecules in solid are closely packed and in fixed positions. The
molecules can vibrate but do not move around which keeps the shape
and volume definite.
(b) Liquids have no definite shape but definite volume because the
molecules in liquid are not so closely packed and they have space
between them. The molecules can move around and the forces of
attraction between molecules is less as compared to solids, so the liquid
takes the shape of the container and volume is definite.
(c) Gases do not have a definite shape or volume because the molecules
in gases are very loosely packed, they have large intermolecular spaces
and hence they move around. The force of attraction between molecules
is also very less, as a result gases acquire any shape or any volume.
3. Why is glass considered a super cooled liquids?
Glass is an inorganic solid and non-crystalline material that is transparent in appearance. It is produced
by combining silica, calcium carbonate and sodium carbonate. Few properties of glass are listed below:
It is a material made of natural products.
It is an inorganic solid material.
Glass can withstand high temperatures.
Glass is a supercooled liquid
Glass is called supercooled liquid because glass is an amorphous solid. The tendency for amorphous solids to
flow. Therefore it is assumed liquid that is supercooled. Glass is often referred to as a supercooled liquid because
it does not deliver a crystalline structure, but instead forms an amorphous solid that enables molecules to
continue to transit in the substance.
3. . Ionic solids conduct electricity in molten state but not in solid state. Explain?
Yes. Ionic solids conduct electricity in a molten state but not in solids state.This is because,
in ionic compounds, electricity is conducted by ions. In contrast, ions are held together by
strong electrostatic forces in a solid-state and are not free to move about within the solid.
Hence, in molten state or solution form, the ions are free to move and conduct electricity.
4. What is unit cell ?
The smallest repeating unit of the crystal lattice is the unit cell, the building block
of a crystal. A unit cell is the smallest portion of a crystal lattice that shows the three-
dimensional pattern of the entire crystal. A crystal can be thought of as the same unit cell repeated
over and over in three dimensions.
5. Write the type of unit cell.
There are 4 types of unit cell:
- Primitive (P)
- Body – centered (I)
- Face – Centered (F)
- Side – Centered (C)
6. Give the significant of lacttice point?
The significance of a lattice point is that each lattice point represents one constituent particle
of a solid which may be an atom, a molecule (group of atoms), or an ion. Lattice point is the
position in the unit cell or in a crystal where the probability of finding an atom or an ion is the highest.
7. Name parameters that characterize a unit cell?
The six parameters that characterize a unit cell are as follows.
(i) Its dimensions along the three edges, a, b, and c These edges may or may not be equal.
(ii) Angles between the edges These are the angles (between edges b and c is α), (between
edges a and c is β), and (between edges a and b is γ).
8. Distinguish between: (i) Hexagonal and monoclinic unit cells (ii) Face-centered and end –
centered unit cell.
Hexagonal and monoclinic unit cells:-
Properties Hexagonal Monoclinic
Possible Variation Primitive Primitive, End centered
Axial distance
Axial angles
Examples Graphite, ZnO Monoclinic sulphur
(ii) Face-centred and end-centred unit cells:-
A face-centred unit cell contains atoms at all the corners and at the centre of all the faces,
whereas in end - centred unit cell one pair of opposite faces contains atoms apart from atoms
at all the corners.
9. Explain how much portion of an atom located at (i) corner and (ii) body
centre Of a cubic unit cell is part of its neighboring unit cell.
(i) An atom located at the corner of a cubic unit cell is shared by eight
adjacent unit cells. Therefore,1/8th portion of the atom is shared by one
unit cell. (ii) An atom located at the body centre of a cubic unit cell is not
shared by its neighbouring unit cell. Therefore, the atom belongs only to
the unit cell in which it is present i.e.,its contribution to the unit cell is 1.
10. What is coordination number?
Coordination number, also called Ligand, the number of spheres with which a sphere
has direct contact in closed packed structure.
11. In terms of band theory, what is the difference? (i) Between a conductor
and a insulator (ii) Between a conductor and a semiconductor.
The differences are given below:
(i) Conductor and insulator
In conductor, the valence band is partially filled and it overlaps with a
high energy unoccupied conduction band.
Electrons can easily flow under an applied electric field.
In case of insulator, the valence band is fully-filled and there is large
energy gap between the valence band and the conduction band.
(ii) Conductor and semiconductor
In conductor, the valence band is partially filled and it overlaps with a
high energy unoccupied conduction band.
Electrons can easily flow under an applied electric field.
In semiconductor, the valence band is filled and there is a small gap
between the valence band and the next higher conduction band.
Some electrons can jump from the valence band to the conduction band
and conduct electricity
12. Silver crystallizes in fcc lattice. If the edge length of the cell is 4.07 x 10-8 cm and
density is 10.5 g/cm -3 .Calculate the atomic mass of silver.
n. M 4. M g
=D= =¿ M =106 , 59.( )
13. Niobium crystallizes in body centered cubic structure. if density is 8.55
N A .V unit cell −23 −8
6,023.1 0 .( 4 , 07.1 0 ) mol
g/cm3 . Calculate atomic radius of niobium using atomic mass of silver.
3. M . P 3.93 .68 % −8
D= 3
= 3 23
=8 , 55=¿ R=2,064.1 0 (cm)
4 п R . N A 4. п. R .6,023 .10
14. What is crystalline?
A crystalline solid is a type of solid whose fundamental three-dimensional
structure consists of a highly regular pattern of atoms or molecules, forming
a crystal lattice. The majority of solids are crystalline solids, and the
different arrangements of atoms and molecules within them can change their
properties and appearance.
15. What is amorphous solids?
Another type of solid is an amorphous solid, which does not have a periodic pattern. The atoms
and molecules within amorphous solids are largely disorganized. Because of this, they share
many similarities to liquids, and in fact have no set melting point. Instead, because the distances
between neighboring atoms or molecules in the structure vary, thermal energy passes through the
material unevenly. The material melts slowly over a large range of temperatures.
14 . What are the differences between crystalline and amorphous solids?
- Crystalline solid are anisotropic in nature, while amorphous solids posses
isotropism.
- Crystalline solids posses a sharper melting point, while the amorphous
solids melt over a wide range of different temperatures.
- Crystalline solids are circular structure while amorphous solids are not
circular structure.
Difference between Crystalline and Amorphous
CRYSTALLINE SOLIDS AMORPHOUS SOLIDS
Atoms are arranged in regular 3 dimension They do not have regular arrangement
Sharp melting point No particular melting point
Anisotropic Isotropic
True solid Pseudo solid
Symmetrical Unsymmetrical
More rigid Less rigid
Long range order Short range order
Example: Potassium nitrate, copper Example: Cellophane, polyvinyl chloride
15. What is Schottky defect and Frenkle defect?
Schottky defect:
Schottky defects occur in ionic crystals where the size of anion is almost
same with the size of the cation.
One anion and one cation leave the crystal at the same time to create
Schottky defect. None of them occupies the interstitial site again.
One Schottky defect leads to the formation of two vacancies.
Electrical neutrality of the whole crystal is maintained.
Density of the crystal decreases for Schottky defects as vacancies are
created.
Frenkel defect:
In Frenkel Defect, neither any atom leaves the solid crystal nor do any
foreign atoms occupy any interstitial position. So the overall density of
the crystal solid remains unchanged.
This type of defect is usually observed in ionic crystals, where size of
anion is substantially larger than the size of cation. For example: zinc
sulfide (ZnS), silver chloride (AgCl), etc.
The smaller ions, usually cation, move from original lattice site to
interstitial position; while, the larger ions (anion) remain in their
corresponding lattice sites.
It does not affect the chemical property of the solid.
Electrical neutrality is also maintained in this defect.
16. What are the Similarities Between HCP and CCP?
Both HCP and CCP has spheres with 12 neighbouring spheres.
Both HCP and CCP crystal systems have around 74% of its volume occupied by
spheres or atoms whereas 26% of the volume is occupied by empty spaces.
17. Different between CCP and HCP?
HCP and CCP are two forms of crystal structures. The difference between HCP and CCP is
that, In HCP crystal systems, the third layer of spheres has the same arrangement of spheres
as in the first layer; hence, spheres of the second layer cover the tetrahedral holes of first
layer and the third layer whereas in CCP crystal systems, the second layer of spheres is
placed on to half of the depressions of the first layer, and the third layer is completely different
from that of the first two layers; the third layer is stacked in the depressions of the second
layer.
18. What is solution solid?
A solid solution is a uniform mixture of two crystalline solids that share a common crystal
lattice. Solid solutions often consist of two or more types of atoms or molecules that share a
crystal lattice, as in certain metal alloys. Solvent is the element or compound that is present in the
greatest amount. Solute is used to denote an element or compound present in a minor
concentration. The solute may incorporate into the solvent crystal lattice substitutionally, by
replacing a solvent particle in the lattice, or interstitially, by fitting into the space between solvent
particles. Both of these types of solid solution affect the properties of the material by distorting the
crystal lattice and disrupting the physical and electrical homogeneity of the solvent material.
19. Conditions of Solid State?
- Size of ions, molecules: trang 59, dung dịch rắn liên tục: continuous solution solid
- Valence of ions: When the valency of 2 substituted and substituted ions is the same, it will
easily form a solid solution, while different will create a limited solid solution.
- Chemical reaction: The stronger the tendency towards a chemical reaction between two
crystalline matter, the more limited the ability to form a solid solution
- Types of structure: In order to easily create a continuous solid solution, the two components
must have the same lattice parameters: type of lattice structure, number of structural units,
polarity, distance between ions, valence, coordination number, ionic radius
20. Types of solution solid?
There are 3 types of solution solid: Substitutional Solid Solution, Interstitial Solid Solutions,
latticeless solid solution.
21. What is non-stoichiometric compounds?
The existence of nonstoichiometric compounds is related to the
presence of defects in the lattice structures of crystalline
substances, such as the absence of ions from sites that would
normally be occupied. For example, a sodium chloride crystal that
lacks a sodium ion and a chloride ion is defective, but still
stoichiometric because the numbers of sodium ions and chloride ions
are the same; if the sodium ion site, however, is filled by a neutral
sodium atom, which then gives up its valence electron to fill the
chloride ion site, the crystal defect is remedied, but the crystal is
now nonstoichiometric because it contains more sodium ions than
chloride ions.
