This document provides an overview of solid state structures. It discusses the two main types of solids - crystalline and amorphous - and explains their distinguishing characteristics. Crystalline solids have a definite, orderly arrangement of atoms while amorphous solids do not. The document then covers various topics related to crystalline solids, including crystal structures, unit cells, Bravais lattices, and the structures of materials like NaCl, diamond, and graphite. It also discusses crystal imperfections and different types of defects that can occur in ionic crystals.
Contains information about various crystal types in solid state chemistry like Rock Salt, Wurtzite, Nickel Arsenide, Zinc Blende etc. It also gives a brief description of lattice energy and Born Haber cycle.
Solid state chemistry- laws of crystallography- Miller indices- X ray diffraction- Bragg equation- Spectrophotometer- Determination of interplanar distance- Types of crystal
Contains information about various crystal types in solid state chemistry like Rock Salt, Wurtzite, Nickel Arsenide, Zinc Blende etc. It also gives a brief description of lattice energy and Born Haber cycle.
Solid state chemistry- laws of crystallography- Miller indices- X ray diffraction- Bragg equation- Spectrophotometer- Determination of interplanar distance- Types of crystal
this is a case chapter for class 12 as it was not available on the net however this ppt u won't be able download ...if you personally want it pls contact me on ritik.tatia@gmail.com .......
Solids - Arrangement of solid particlesSidra Javed
In solids, molecules, ions or atoms are arranged in a definite pattern. Packing arrangement of particles is responsible for different types of solids and their properties
this is a case chapter for class 12 as it was not available on the net however this ppt u won't be able download ...if you personally want it pls contact me on ritik.tatia@gmail.com .......
Solids - Arrangement of solid particlesSidra Javed
In solids, molecules, ions or atoms are arranged in a definite pattern. Packing arrangement of particles is responsible for different types of solids and their properties
The crystal structure notes gives the basic understanding about the different structures crystalline materials and their properties and physics of crystals. It also throw light on the basics of crystal diffraction
Crystal Material, Non-Crystalline Material, Crystal Structure, Space Lattice, Unit Cell, Crystal Systems, and Bravais Lattices, Simple Cubic Lattice, Body-Centered Cubic Structure, Face centered cubic structure, No of Atoms per Unit Cell, Atomic Radius, Atomic Packing Factor, Coordination Number, Crystal Defects, Point Defects, Line Defects, Planar Defects, Volume Defects.
The study of crystal geometry helps to understand the behaviour of solids and their
mechanical,
electrical,
magnetic
optical and
Metallurgical properties
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
2. INTRODUCTION
• The state of matter in which materials retain their boundaries without
support, the atoms or molecules occupying fixed positions with respect
to each other and unable to move freely.
• Cause of existence of substance as solid are –
1. Intermolecular forces
2. Thermal energy
• Study of structure of crystalline solid and their properties is know as
Crystallography
• There are broadly two type of solid - Crystalline solid and Amorphous
solid depending upon their structure.
3. Preview
We are going to cover the following topic in this
module.
1. Types of solid
2. Crystal structure
3. Crystal lattice and unit cell
4. Cubic crystals
5. Structure of graphite
6. Structure of NaCl
7. Structure of diamond
8. Crystal imperfection
9. Conclusion
4. TYPES OF SOLIDS
Crystalline solid
They have definite and regular geometry due
to definite and orderly arrangement of atoms,
ions or molecules in three-dimensional
space.
They have sharp melting points and change
abruptly into liquids.
Crystalline solids are anisotropic.
These are considered as true solids
Example: NaCl, KCl, Sugar, Quartz, etc.
Amorphous solids
They do not have any pattern of arrangement
of atoms, ions or molecules and, thus do not
have any definite geometrical shape.
Amorphous solids do not have sharp melting
point and do not change abruptly into liquids.
Amorphous solids are isotropic
These are considered pseudo solids or
supercooled liquid.
Example :Plastic, Glass, Rubber etc
There are basically two types of solids on the basis of molecular arrangement
1. Crystalline solids
2. Amorphous solid
6. Radius Ratio of Ionic Crystals
Ionic solids posses different coordination number, because of differences in the number and relative sizes of the
cations and anions. Larger the size of anion, greater will be the number of cations which can be packed in a unit
cell.
Radius Ratio is the ratio of the cation to that of the anion in an ionic solid. Thus, radius ratio is
Radius of cation / radius of anion = r
7. Crystal lattices and lattice cell
• Crystal lattice is a highly ordered three dimensional structure, formed by its constituent atom
or molecule or ions. Lattice is regarded an infinite set of point repeated regularly throughout
space.
• Unit cell is the smallest building unit in space of crystal, which when repeated over and over
again in three dimensions, result in a space lattice of the crystalline substance.
The unit cell in a three dimensional lattice is characterised
by the length and angle. These are collectively know as the
Unit cell parameters.
From the variation in these parameter, a total of seven
Crystal lattice can be constructed. These different unit cell
are know as Bravais lattices.
9. Cubic CrystalsIn a cubic crystal , the intercept on three axes are equal and all the angle are equal to 90 degree.
A cubic crystal can be any of the following three types
1. Simple or primitive crystal lattice (SC)
2. Body centred crystal lattice (BCC)
3. Face centred crystal lattice (FCC)
(i) SIMPLE CRYSTAL LATTICE – In simple crystal
lattice there are lattice point at the eight corners of the
unit cell. In a simple cubic structure, an atom
situated at any corner of each unit is shared by
a total of eight unit cell , thus , each unit cell
has 1/8 th share of every corner atom.
So the total contribution of all the eight corner
atom is equal to 1.
= 8 x 1/8 = 1atom/ unit cell of SC
10. (ii)BODY CENTRED CRYSTAL LATTICE –
In the body centred crystal lattice, there are lattice
points at eight corner and at the centre of the unit cell
The atom at the centre is independent of other cell,
while each of the eight atoms situated at the corners
is shared by total of eight unit cells. Thus , the total
number of atom per unit cell
= 1( at the centre) + 8 x 1/8 ( at the corners)
= 1 + 1 = 2 atom/ unit cell of BCC
(iii) FACE CENTRED CRYSTAL LATTICE –
In the face centred crystal lattice, there are lattice points
at the centre of all faces, in addition to those at the eight
Corner of the unit cell. Every atom situated at the centre of
a face of a unit cell is shared by two adjoining unit cell.
Thus, the total number of atom per unit cell
= 1/2 x 6 ( at the centre of face) +
8 x 1/8 (at the corner)
= 3+1 = 4 atom/ unit cell of FCC
11. Coordination Number of a cubic lattice
The total number of nearest neighbour atoms of a particular atom in a crystal lattice, is called
Coordination Number
(i) Simple cubic cell (SC) – In such a
cell, there are six atom which are the nearest
neighbour for every corner atom.
Hence , the coordination is 6
(ii) Body centred cell (BCC) - In this, an atom
in the centre of the cell has all the eight corner atoms as
its close neighbours.
Hence, the coordination number is 8
12. (iii) Face centred cell (FCC) –
In this , each atom is in direct contact with 12 nearest neighbours – 6 of which lies in one
layer in the same plane , 3 from layer above and 3 from layer below. Hence, the
coordination number is 12
this structure is akin to tetrahedral structure.
Cu, Au, Al crystallize in fcc lattice.
13. Radius Ratio of Ionic Crystals
• Ionic solids posses different coordination number, because of different in the number and relative
sizes of the cation and anion.
• Radius Ratio is the ratio of the cation radius to the anion in an ionic solid. Thus radius ratio is
radius of cation / radius of anion = r+/ R-
• From the value of radius ratio, one can know
the coordination number and hence
predict the shape of solid
• Higher the radius ratio, larger is the size
of the cation and hence , greater is its
co-ordination number.
14. CALCULATION OF DENSITY OF CUBIC CRYSTAL
Let Z be the number of atom in unit cell ; M be the atomic mass and A be the edge
length of the crystal
volume of unit cell = A3
mass of the unit cell = ( no. of the atom per unit cell ) x [ mass of the each
atom ]
= Z x (M/Na )
Density = Mass of the unit cell/ volume of the unit cell
= Z M/ A3 Na
15. Structure of graphite
• There is planar ( sp2 – Hybridisation ) arrangement and every
carbon atom is bounded to three other carbon atoms,
forming the hexagonal network sheet ( like those in benzene
rings )
• The distance between two carbon atom in a layer is 1.42 A0
• The hexagonal layers are held parallel by weak van der waals
forces
• The distance the layer is 3.40 Ao
• Due to weak force between the layer , graphite is soft,
slippery and flaky in nature.
•
16. • NaCl has a cubic unit cell.
• It is best thought of as a face-centered
cubic array of anions with an
interpenetrating fcc cation lattice
(or vice-versa).
• The cell looks the same whether you start
with anions or cations on the corners.
• Each ion is 6-coordinate and has a local
octahedral geometry.
STRUCTURE OF NaCl
17. STRUCTURE OF DIAMOND
• Diamond is a metastable allotrope of
carbon.
• Each carbon atom is sp3 hybridised and
have tetrahedral structure
• The distance between two carbon is 1.54 Ao
• Each carbon atom is bonded covalently
with other surrounding four carbon atoms
and are arranged in a variation of the face
centred cubic crystal structure called a
diamond lattice .
18. CRYSTAL IMPERFECTIONS
• Imperfections in ionic crystals means any deviation from the perfectly ordered
arrangement of the constituent ions of the crystal , thereby resulting in change in
the properties.
• Electronic imperfections-which correspond to defects in ionic crystals , thereby
resulting in change in the properties.
• Atomic impurities-arise due to irregularity in the arrangement of atoms or ions in
the crystal lattice.
• There are two type of point imperfection in ionic crystal
1. Stoichiometric defect
2. Non – stoichiometric defect
20. Non stoichiometric defect
Metal ion deficiency defect
due to missing cation.
Metal ions deficiency defect
due to presence of an
impurity ion or higher
valency.
Metal ions
excess defect
due to extra
interstitial cation
Metal ion excess
defect due to
vacancies
