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1、材料科学基础Fundamental of Materials ScienceProf: Tian Min Bo Tel: 62795426 ， E-mail: Department of Material Science and EngineeringTsinghua University. Beijing 100084Lesson one1Materials Science deals with the relationship between the macroscopic properties and the microscopic structures.2 2 The principa
2、l goals of a materials scientist and engineer are to make existing materials better and to invent or discover phenomena that will allow development of new materials, devices, and applications. All engineers, in all specialties can benefit from a thorough knowledge of materials science.3 3 chemical m
3、echanical physical metallurgical electron crystal phase metallographicalAll the properties of the materials, without exception, can be found their causes from their structures.macroscopic propertiesmicroscopic properties4 41.1 Atomic Structure1.1.1 Atomic numbers and atomic masses 1. Atomic models 1
4、. Atomic modelsChapter 1Atomic Structure and Bonding5 52. Atomic numbers The atomic number of an atom indicates the number of protons (positively charged particles) which are in its nucleus, and in a neutral atom the atomic number is also equal to the number of electrons in its charge cloud. All the
5、 elements have been classified according to electron configuration in the periodic table.6 6The periodic tableThe periodic table7 73. Atomic mass The relative atomic mass of an element is the mass in grams of 6.0231023 atoms (Avogadros number NA) of that element.8 81.1.2 The electronic structure of
6、atoms 1. Quantum numbers 1. Quantum numbers Quantum numbers are the numbers in an atom Quantum numbers are the numbers in an atom that assign electrons to discrete energy levels.that assign electrons to discrete energy levels. The energy level to which each electron The energy level to which each el
7、ectron belongs is determined by four quantum numbers.belongs is determined by four quantum numbers. The principal quantum number n The subsidiary azimuthal quantum number l The magnetic quantum number ml Electron spin quantum number ms9 9 n refers to the quantum shell to which the electron belongs.
8、The number of energy levels in each quantum shell is determined by the azimuthal quantum number l and the magnetic quantum ml. The magnetic quantum number ml gives the number of energy level, or orbitals, for each azimuthal quantum number. ms = K shell for n = 1; L shell for n = 2; M shell for n = 3
9、 and so onl = 0,1,2,3 n-1s for l = 0; p for l = 1; d for l =2 ; f for l = 3 and so on.ml = 2l +1 , l 0l10102. Electron configurations. Electron configurations Pauli exclusion principlePauli exclusion principle This principle stipulates that each electron This principle stipulates that each electron
10、state can hold no more than two electrons, state can hold no more than two electrons, which must have opposite spins.which must have opposite spins.1111KLMNOPsssssspppppddddfff1212The complete set of quantum numbers for each of The complete set of quantum numbers for each of the 11 electrons in sodi
11、um.the 11 electrons in sodium.electron 11 n = 3, l = 0, ml = 0, ms = + or -electron 10 n = 2, l = 1, ml = +1, ms = -electron 9 n = 2, l = 1, ml = +1, ms = + electron 8 n = 2, l = 1, ml = 0, ms = - electron 7 n = 2, l = 1, ml = 0, ms = + electron 6 n = 2, l = 1, ml = -1, ms = - electron 5 n = 2, l =
12、1, ml = -1, ms = + electron 4 n = 2, l = 0, ml = 0, ms = - electron 3 n = 2, l = 0, ml = 0, ms = + electron 2 n = 1, l = 0, ml = 0, ms = - electron 1 n = 1, l = 0, ml = 0, ms = + 3s12p62s21s21313The pattern used to assign electrons to energy The pattern used to assign electrons to energy levels.leve
13、ls.1414ffffdddddpspspspspspss1515 Electrons with the same subsidiary quantum number have as many parallel spins as possible.16163. Atomic size. Atomic size17174. Electronegativity. Electronegativity Electronegative elements are nonmetallic in nature and accept electrons in chemical reactions to prod
14、uce negative ions, or anions. Electronegativity describes the tendency of an atom to gain an electron.PositivecationNegativeAnion1818191920201.1. Calculate the energy in joules(J) and electron volts(eV) of the photon whose wavelength is 121.6 nanometers (nm). (1.00eV=1.6010-19 J ; h = 6.6310-34 Js ;
15、 1 nm = 10-9 m)Solution:Solution:Examples and Discussions21212.2. Electron transfer from Na to Cl creates a cation (Na+) and an anion (Cl). The ionic bond is due to the coulombic attraction between the ions of opposite charge. (1) Compare the electronic configuration for the atoms (Na, Cl) and ions
16、(Na+, Cl). (2) Which noble gas atoms have electronic configurations equivalent to those for the Na+ and Cl.Solution:Solution:(1) Na: 1s22s22p63s111Cl: 1s22s22p63s23p517 Because Na loses its outer orbital (3s) electron in becoming Na+,2222Na: 1s22s22p6Because Cl gains an outer orbital electron in bec
17、oming Cl, its 3p shell becomes filled: Cl: 1s22s22p63s23p6(2) Ne: 1s22s22p6 10 equivalent to Na (of course, the nuclei of Ne and Na differ)Ar: 1s22s22p63s23p6 18 equivalent to Cl (again, the nuclei differ).232324243.3. Using the electronic structures, compare the electronegativities of calcium and b
18、romine.Solution:Solution:The electronic structure, obtained from Appendix C, are:Ca: 1s2 2s2 2p6 3s2 3p6Br: 1s2 2s2 2p6 3s2 3p6 3d104s24s2 4p5Calcium has two electrons in its outer 4s orbital and bromine has seven electrons in its outer 4s4p orbital. Calcium, with an electronegativity of 1.0, tends
19、to give up electrons and has low electronegativity, but bromine, with an electronegativity of 2.8, tends to accept electrons and is strongly electronegative. This difference in electronegativity values suggests that these elements may react readily to form a compound.25254.4. Calculate the number of
20、 electrons capable of conducting an electrical charge in ten cubic centimeters of silver.Solution:Solution:The valence of silver is one, and only the valence electrons are expected to conduct the electrical charge. From Appendix A, we find that the density of silver is 10.49 g/cm3. The atomic mass o
21、f silver is 107.868 g/mol.Mass of 10 cm3 = (10 cm3)(10.49 g/cm3) = 104.9 g2626Exercise1 1 What is the mass in grams of one atom of copper? How many copper atoms are in 1 g of copper?2 2 Write the electron configurations of the elements: (1) iron, Z=26 ; (2) samarium, Z=623 3 Write the electron confi
22、guration for the Fe atom (Z=26) and the Fe2+ and Fe3+ ions by using conventional spdf notation.27274 4 A hydrogen atom exists with its electron in the n=3 state. The electron under goes a transition to the n=2 state. Calculate:(1) the energy of the photon emitted ;(2) its frequency ;(3) its wavelength ;(4) is energy emitted or absorbed in the transition?2828Thank you !1 2929
