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INTRODUCTION TO CERAMIC MINERALS

INTRODUCTION TO CERAMIC MINERALS

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INTRODUCTION TO CERAMIC MINERALS

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  1. INTRODUCTION TO CERAMIC MINERALS LECTURE #2 DEFINITION OF CRYSTAL The body ACHIEVES what the mind believes

  2. LEARNING OUTCOME At the end of the lesson, students should be able to : • Write the definition of crystal. • Recognize crystal material and non-crystal material. • Explain the concept of the planetary atoms. • Draw the electrons arrangement in atom if atomic number is given. • Explain how atoms turn out to be cation or anion. • Explain the group and period trends in the periodic table. The body ACHIEVES what the mind believes

  3. CRYSTALS • Crystals are solids that form by a regular repeated pattern of molecules connecting together. • In some solids, the arrangements of the building blocks (atoms and molecules) can be random or very different throughout the material. • In crystals, a collection of atoms called the Unit Cell is repeated in exactly the same arrangement over and over throughout the entire material. The body ACHIEVES what the mind believes

  4. CRYSTALS - Cont… • Something is crystalline if the atoms or ions that compose it are arranged in a regular way (i.e. a crystal has internal order due to the periodic arrangement of atoms in three dimensions). • Gems are described as amorphous if they are non-crystalline. The body ACHIEVES what the mind believes

  5. DEFINITION OF CRYSTAL - Recall… Which of the following are crystalline? The body ACHIEVES what the mind believes

  6. CRYSTAL LATTICE • A crystal structure is a three dimensional pattern of atom or ions in space • It is composed of a unit cell, a set of atoms arranged in a particular way; which is periodically repeated in three dimensions on a lattice. • The spacing between unit cells in various directions is called its lattice parameters. The body ACHIEVES what the mind believes

  7. CRYSTAL LATTICE - Cont… • The symmetry properties of the crystal are embodied in its space group. • A crystal’s structure and symmetry play a role in determining many of its properties, such as cleavage, electronic band structure, and optical properties. The body ACHIEVES what the mind believes

  8. UNIT CELL • Unit cell – the smallest unit of a mineral that possesses the symmetry and properties of the mineral. The body ACHIEVES what the mind believes

  9. UNIT CELL • Small group of atom (4~1000) that have a fixed geometry relative to another. • Spatialarrangement of atoms which is tiled in three-dimensional space to describe the crystal. The body ACHIEVES what the mind believes

  10. UNIT CELL - Cont… • The atoms are arranged in a ‘box’ with parallel sides called the unit cell which is repeated by simple translation to make up the crystal. • The atoms may be at the corners, on the edges, on the faces, or wholly enclosed in the box, and each cell in the crystal is identical. The body ACHIEVES what the mind believes

  11. UNIT CELL - Cont… • This is what was meant by an ‘order internal arrangement’. • It is a reason why crystal have such nice faces, cleavages, and regular properties. The body ACHIEVES what the mind believes

  12. UNIT CELL - Cont… • The unit cell is given by its lattice parameters : • The position of the atoms inside the unit cell are described by the set of atomic positions (xi, yi, zi), measured from the lattice point. The body ACHIEVES what the mind believes

  13. UNIT CELL - Cont… • The box of the unit cell is a parallel-piped with no constraints on the lengths of the axes or the angles between the axes. • The box is defined by three axes or cell edges, a, b, and c and the three inter-axial angle alpha, beta, and gamma, such that alpha is the angle between b and c, beta between a and c, and gamma between a and b. The body ACHIEVES what the mind believes

  14. UNIT CELL - Cont… • For each crystal structure there is a conventional unit cell, which is the smallest unit that has the full symmetry of the crystal (Figure 9) • However the conventional unit cell is not always the smallest possible choice. • A primitive unit cell of a particular crystal structure is the smallest possible unit cell one such that, when tiled, it completely fills space. The body ACHIEVES what the mind believes

  15. UNIT CELL Can you see the FCC structure arrangement in the above Figure 9? Figure 9 The body ACHIEVES what the mind believes

  16. LATTICE • A lattice is an imaginative pattern of points in which every point has an environment that is identical to that of any other point in the pattern. • A lattice has no specific origin as it can be shifted parallel to itself. The body ACHIEVES what the mind believes

  17. LATTICE - Cont… • A row represents equally spaced points along a line. • A plane lattice or net represents a regular arrangement of points in two-dimensions and a space lattice depicts the distribution of equivalent points in three-dimensions. The body ACHIEVES what the mind believes

  18. UNIT CELL - Cont… Lattice is a set of points or grid lines that possess the translational periodicity of the crystal --imaginary construct The body ACHIEVES what the mind believes

  19. Different Ways of Choosing a Unit Cell

  20. Different Ways of Choosing a Unit Cell

  21. LATTICE - Cont… • There are only five types of plane lattices: • Parallelogram, a ≠ b, γ≠ 90° • Rectangular, a ≠ b, γ = 90° • Diamond, a1 = a2, γ≠ 90°, 60° or 120° • Rhombus, a1 = a2, γ = 60° or 120° • Square, a1 = a2, γ = 90° • The most general two-dimensional lattice is a parallelogram net (Figure 10). The body ACHIEVES what the mind believes

  22. LATTICE – cont… Figure 10 : Five types of plane lattice. The body ACHIEVES what the mind believes

  23. THE BRAVAIS LATTICE • It is a combinations of the crystal systems with the various possible lattice centering. • It describe the geometric arrangement of the lattice points, and thereby the translational symmetry of the crystal. • In three dimensions, there are 14 unique Bravais Lattice with are distinct from one another in the translational symmetry they contain. • Also known as space lattices. The body ACHIEVES what the mind believes

  24. THE BRAVAIS LATTICE The body ACHIEVES what the mind believes

  25. DEFINITION OF CRYSTAL CHEMISTRY The body ACHIEVES what the mind believes

  26. DEFINITION OF CRYSTAL CHEMISTRY • This is a subject relating the : • chemistry of minerals to their structure • crystallography • physical properties • atoms arrangement • Must consider some of elementary concepts of atoms and ions and their bonding forces in crystalline materials. The body ACHIEVES what the mind believes

  27. WHAT IS THE DIFFERENCE BETWEEN A CRYSTAL AND A MOLECULE? • Must know term ‘bonding’ – some of simple mechanisms between atom which cause them to be attracted to each other and create solid matter. • 3 categories of atomic bonding : The body ACHIEVES what the mind believes

  28. ATOMS AND PERIODIC TABLE • Atoms – smallest subdivision of matter that retain the characteristics of the elements. • They consist of a very small, massive nucleus composed of protons, neutrons and surrounded by a much larger region thinly populated by electrons. • The smallest atom is hydrogen that has a radius of only 0.46Å • The largest is cesium with radius of 2.62Å The body ACHIEVES what the mind believes

  29. ATOMS AND PERIODIC TABLE • Every atom consists of a small nucleus composed of protons and neutrons, which is encircled by moving electrons in their orbitals, specific energy levels. • In an atom, there will be always equal number of protons and electrons • The top most orbital electrons, valence electrons, affect most material properties that are of interest to engineer. E.g.: chemical properties, nature of bonding, size of atom, optical/ magnetic/ electrical properties.

  30. ATOMS AND PERIODIC TABLE • Electrons and protons are negative and positive charges of the same magnitude being 1.60x10-19 coulombs. • Neutrons are electrically neutral. • Protons and neutrons have approximately the mass, 1.67x10-24 g, which is larger than that of an electron, 9.11x10-28g.

  31. ATOMS AND PERIODIC TABLE

  32. ATOMS AND PERIODIC TABLE Element: Fluorine Z=9 Electron: 9 Proton: 9 Neutron: 10 Atomic mass:19

  33. ATOMS AND PERIODIC TABLE • Ion : any atom or molecule with net charge • Cation: an ion with a positive charge • Anion: an ion with a negative charge • Valence electron: electrons in the outermost shell which are most involved in bonding • Atomic radius : distance from the center of an atom's nucleus to its outer most electron • Electronegativity : the measure of an atoms attraction for electrons in a chemical bond

  34. ATOMS AND PERIODIC TABLE • Ionization energy: the energy required to remove an electron from an atom or ion. • Atomic number: the number of protons in the nucleus of an atom of an element • Atomic mass: the number of protons and neutrons in the nucleus • Electron configuration: the distribution of all the electrons in an atom according to their atomic orbit

  35. ATOMS AND PERIODIC TABLE • Isotopes : Atoms of the same electron but with differing numbers of neutron • Atomic number: the number of protons in the nucleus of an atom of an element • Electron configuration: the distribution of all the electrons in an atom according to their atomic orbit

  36. ATOMS AND PERIODIC TABLE • The valence shell: is the outermost shell of an atom, which contains the electrons most likely to account for the nature of any reactions involving the atom and of the bonding interactions it has with other atoms

  37. ATOMS AND PERIODIC TABLE The periodic table provides information about each element. • atomic number • symbol • name • average atomic mass • electron configuration

  38. ATOMS AND PERIODIC TABLE - Cont… • Neil Bohr (1912) – develop concept of the ‘planetary’ atom in which the electrons are visualized as circling the nucleus in ‘orbits’ or energy levels at distance from the nucleus depending on the energies of the electrons. The body ACHIEVES what the mind believes

  39. ATOMS AND PERIODIC TABLE - Cont… • Electrons are restricted to specific energy level or orbital shells, which differ from each other by discrete amounts of energy, or quanta. • The innermost shell, closest to the nucleus, is designated the K-shell (n=1) and contain a maximum of two electrons. • Outer orbitals representing higher energy level are designated as L (n=2), M (n=3), N (n=4) and so forth. The body ACHIEVES what the mind believes

  40. ATOMS AND PERIODIC TABLE - Cont… • The L-shell (8 e-), M-shell (18 e-), N-shell (32 e-). • The higher shells are not completely filled. • Sub-shells of different energy occur within a specific shell. Such sub-shells, listed in order of increasing energy, are s, p, d, and f. The body ACHIEVES what the mind believes

  41. The body ACHIEVES what the mind believes

  42. PERIODIC TABLE: Electron configuration H(Z=1) : 1s He(Z=2) : 1s2 Na(Z=11) : 1s22s22p63s1 Fe(Z=26) : 1s22s22p63s23p63d64s2 The body ACHIEVES what the mind believes

  43. PERIODIC TABLE • The fundamental difference between atoms of the different elements lies in the electrical charge of the nucleus. • The +ve charge is the same as the number of protons. • The number is equal to the number of electrons in an uncharged atom and called atomic number (z). The body ACHIEVES what the mind believes

  44. PERIODIC TABLE • The sum of protons and neutron determines the characteristic mass, or mass number of an element. • Atoms of the same electron but with differing numbers of neutron are called isotopes. • Same Z , but different A – refer to nucleus - Carbon: 12C , 14C - Hidrogen: 1H, 2H, 3H ( hidrogen–no neutron, deuterium- one neutron, tritium- two neutron ) The body ACHIEVES what the mind believes

  45. PERIODIC TABLE - Cont… • The elements in the periodic table are arranged according to increasing atomic number (z). • The atomic weight of an element is a number expressing its relative weight in term of the weight of the element oxygen, which is taken as 16. • A close relationship exists between the electronic structure of an atom, the chemical properties of the element and its place in the periodic table. The body ACHIEVES what the mind believes

  46. PERIODIC TABLE - Cont… • In group Ia, IIa, IIIb, Ivb, Vb, VIb, and VIIa, the number of electrons in the outmost shell is the same for the atoms of each element in a group and is equal to the group number. • Change in ionic sizes are also regularly reflected by the arrangement of the element in the periodic table. • For elements of the same group the ionic radii increase as the atomic number increase. The body ACHIEVES what the mind believes

  47. PERIODIC TABLE - Cont… • E.g. in group IIa the smallest ion is Be2+ with radius of 0.35Å and the largest ions is Ra2+ with a radius of 1.43Å. • As a result of the increasing of nuclear charge, an increase attraction is exerted on outer electron, which causes an effective decrease in ionic radius. The body ACHIEVES what the mind believes

  48. PERIODIC TABLE - Cont… • For +ve ions with the same electronic structure, the radii decrease with increasing charge. E.g. Na+ (0.97Å) and Cl7+ (0.27Å). • The size of ions with similar electron configuration decreases because the increased nuclear charge exerts a greater pull on the electrons, thus decreasing the effective radius of the ion. The body ACHIEVES what the mind believes

  49. IA IIA IIIA IVA VA VIA VIIA VIII IB IIIB IVB VB VIB VIIB IIB PERIODIC TABLE All the elements are classified according to electron configuration in the periodic table. • Elements arrayed in a given column or group have similar valence electron structure, as well as chemical and physical properties. • Group 0 : inert gas. • Group IIIB  IIB : transition metals. • Group IA & IIA are alkali and alkaline earth metals. • Group IIA, IVA, and VA : intermediate between metal and non metals • Group VII A : halogens