L1 Material Chemistry WB

8/11/2019 L1 Material Chemistry WB

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HNC Lecture 1Material Chemistry

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Historically

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Historically

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Historically: only 4 Elements

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Historically

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Historically

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l h


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Material Chemistry

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Nomenclature

Composition

Isotropic / Anisotropic

Allotropic (Carbon Iron, .. )

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Matter

Solids have a defined shapeand volume

Liquids have a fixed volumebut flow to assume the shapeof their containers

Gases completely fill theircontainers, regardless ofvolume.

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P ti f M tt


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Properties of Matter

Because they differ insize, the two samples ofsulfur have differentextensive properties, such

as mass and volume 27

In contrast, theirproperties, includinmelting point, andelectrical conductiv

identical


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Material Chemistry

Matter , is anything that takes up space and hasmass. Four states of matter are observable ineveryday life: solid , liquid , gas and plasma

An Atom , is the smallest chemical unit of matter

An Element , is a material, which cannot bebroken down, or changed into another substanceusing chemical means

The mass of an object is the quantity of matter itcontains

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Atomic Radii


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Atomic Radii

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Periodic Table

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Periodic Table Clock

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Atom and Electron Shells

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C b d it All t


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Carbon and its Allotropes

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Sub-Atomic ParticlesProton , a stable subatomic particle occurring

in all atomic nuclei, with a positive electriccharge equal in magnitude to that of anelectron

Neutron , a subatomic particle of about the

same mass as a proton but without an electriccharge

Elements that contain different numbers ofneutrons are called isotopes

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Sub-Atomic Particles

An Electron , is a stable subatomic particlewith a charge of negative electricity, foundin all atoms and acting as the primarycarrier of electricity in solids

Only the electrons of atoms interact, sothey determine an atoms chemicalbehaviour

Electrons occupy electron shells

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The Atomic Number , is the number of protons,found in the nucleus of an atom of that element

Valence , the combining capacity of an atom:

Positive , if the atom has electrons to give upNegative , if the atom has spaces to fill

Stable , when outer electron shells contain eight electrons (the octet rule)

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A Valence Electron , is associatedwith an atom and that canparticipate in the formation of achemical bond

It is the electrons in an atomsoutermost shell, that interact withother atoms

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Valence Electrons


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Valence Electrons

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Valence Electrons

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Ions

An Ion , is an atom that has lost orgained an electron

An Anion , is an ion with a negative

charge A Cation , is an ion with a negativecharge

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Understanding Ions


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Understanding Ions

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Understanding Ions


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Understanding Ions

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Understanding Ions


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Understanding Ions

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Understanding Ions


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Understanding Ions

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Chemical Combinations


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A Molecule , is formed when two or moreatoms join together chemically

They are connected together so strongly,that they behave as a single particle

A Compound , is a molecule that containsat least two different atoms

All compounds are molecules, but not allmolecules are compounds

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Chemical Combinations An ALLOY is amacroscopically homogeneous substance, which possessesmetallic properties and iscomposed of two or morespecies of atom, one of whichis a metal

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A Mixture , is made from different

substances, that are not chemically joined (separable)

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Ch i l B di g


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Chemical Bonding

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Ch i l B di g


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Chemical BondingPrimary Bonds , involve sharing or donating

electrons between atoms to form a more stableelectron configuration

Secondary Bonds , are due to the attractions ofelectric dipoles in atoms or molecules. Dipoles

are created when positive and negative chargecenters exist. Unlike primary bonding, there isno transfer or sharing of electrons

Weaker than Primary Bonds

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Primar Bonds


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Primary Bonds

Ionic Bonding = transfer of electronsCovalent Bonding = sharing of

electrons between non-metals

Metallic Bonding = the electrostaticforce of attraction between freedelocalised electrons, (the electron seamodel) and positive ions

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Lewis Periodic Table


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Lewis Periodic Table

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Sodium (Na) and Chlorine (Cl)interact by electron transfer

to form an Ionic Bond

Ionic Bonds


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2 ions giving SALT

Covalent Bonds


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Covalent Bonds A covalent bond, forming H 2 ,where two hydrogen atoms sharethe two electrons

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Covalent Bonds


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Covalent Bonds


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Covalent Bonds

Hydrogen atoms can each formone covalent bond, while Carbonatoms can each form four covalentbonds. Four pairs of electrons areshared in a methane molecule CH 4

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Metallic Bonds


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Metallic BondsThe Electron Sea Model

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Secondary Bonds


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Secondary BondsElectronegativity , is a measure, of how

attractive an atom is to electrons (8 is the mnumber)

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Properties of Bonding


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Properties of Bonding

Density

Electrical Conduction

Thermal ConductionDuctility

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Bonding Summary


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Bonding Summary

Density



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Physical Properties


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Physical Properties

Density



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Material Structure


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Material Structure

Crystalline

Amorphous

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Lattice Structure


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Lattice Structure

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Giants Causeway

Crystalline Structure


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Crystalline StructureUnique arrangement of atoms or

molecules in a crystalline liquid or solidHighly ordered structure, occurring due to

the intrinsic nature of molecules, to formsymmetric patterns

Periodic (infinitely repeating, termed long-term order) array of 3D 'boxes', known asunit cells

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The 7 Basic Cell Structures


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The 14 Possible


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Bravais LatticeStructures

Lattice Structure


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Escher

http://www.mcescher.com/gallery/symmetry/

Lattice Structure


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Escher: two possible un

Bravais Lattice


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Robert Hooke

Lo

Example Lattice Structures


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Typical Unit Cell Structure


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Typical Unit Cell Structure

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Amorphous Structure


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p

Any noncrystalline solid in whichthe atoms and molecules are notorganized in a definite latticepattern (no long-term order)

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Amorphous Structure
http://www.britannica.com/EBchecked/topic/553257/solidhttp://www.britannica.com/EBchecked/topic/553257/solid


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p

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Crystal Structures


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Crystal Lattice , the symmetricalthree-dimensional arrangement ofatoms inside a crystal

HCP , Hexagonal Close Packed

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HCP Properties


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Hexagonal unit cell with one atom at

each corner, one at the center of thehexagonal faces, and three in the middle

30 metallic elements have this structure

Ductile enough for some deformation

processes, but not as many as FCCmaterials

More anisotropic than FCC and BCCmaterials

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HCP Applications


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Cubic Crystal Structures


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Cubic

BCC

Body Center

FCC Face Center

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BCC Properties


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Unit cell with one atom at each corner and one inthe middle

21 metallic elements have this structureDuctile, particularly when hot, allowing for

various deformation process

Generally tough at and above room temperature

Exhibits a transition from ductile to brittle at lowtemperatures (see Liberty Boat)

Strength is temperature dependent

Can be hardened with interstitial solutes86

BCC Applications


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FCC PropertiesU i ll i h h d


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Unit cell with one atom at each corner andone at each face

17 metallic elements have this structure

Very ductile when pure, work hardeningrapidly, but softening again when annealed,allowing for various deformation processes

Retain their ductility and toughness atabsolute zero

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FCC Applications


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Number of Atoms per Unit Cell


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Simple Cubic Cell LatticeNearest Neighbours


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Therefore, 6 ch

Packing Density


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FCC Packing Density


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Studentssimple cu

Crystal Structure Summary


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Completedescription ofatomicarrangement

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+

Bravias Lattice

point environment

set of points inspace

=

Basis

atom / m/atom geach lat

Characterisation of Atomic Structure by x- Ray how we know that go

x-Rays have very short wavelength atomic .. measured in Angstroms (

Material Property Classifications


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Mechanical

Electrical

Thermal

Magnetic

Optical

Deteriorative95

Material Characteristics


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Processing

Structure

Properties

Performance

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Solid Materials


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Metals

Ceramics

Polymers

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Metals


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Properties and why they have them?Density



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Ceramics


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Polymers


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Composites


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The Future .. Graphene?The Thinnest material on earth


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The Thinnest material on earth

One atom thick

hence the first 2D materialBest heat conductor

yet fire resistant

Best electrical conductor

200 x stronger than steel*Yet ultra light and incredibly flexible

Impermeable .. enormous potential

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So What?


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Density


Thermal Conduction

DuctilityQuestion .. define the term Metal ?

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Density


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Density


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Density


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Density


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Density


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L1 Material Chemistry WB