Chapter 6. Electronic Structure. Electronic Structure and the Periodic Table ( 전자구조와주기율표 ) 강의개요. 2) The Particle Nature of Light: Photon Energies

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1 Chapter 6 Electronic Structure and the Periodic Table ( 전자구조와주기율표 ) 강의개요 Electronic Structure Electron arrangement in atoms energy levels orbitals electron configurations orbital diagram Periodic Table atomic, ionic radius ionization energy electronegativity Copyright 2005 연세대학교이학계열일반화학및실험 (1) 강의노트 6.1 Light, Photon Energies, and Atomic Spectra 1) The Wave Nature of Light: Wavelength and Frequency Wavelength ( 파장 ; λ) 1 nm=10-9 m Frequency ( 진동수 ; ν) ν = 10 8 s -1 = 10 8 Hz Speed of Light νλ = c = m/s (λ in m: ν in Hz) 2) The Particle Nature of Light: Photon Energies Photon Energy E= SI unit: joule (J), kilojouls (kj) Planck s constant : h= J s 3) Atomic Spectra 전자가높은에너지준위에서낮은에너지준위로이동할때빛을방출하면서생김 quantized energy levels E = E hi - E lo = hν = hc / λ

2 Emission Spectra vs. Energy Levels Na 의노란선, λ = nm 6.2 The Hydrogen Atom 1) Bohr Model 전자는핵주위의고정된반경을가진원형의궤도 (circular orbit of fixed radius) 를따라움직인다. 에너지를흡수하면전자는보다큰에너지를가진높은궤도 (higher orbit) 로이동하며, 전자가다시되돌아오면서에너지를방출한다. 1) Bohr Model (cont.) Energy of the hydrogen electron E n = n = 1,2,3... n : principal quantum number i) zero energy complete separation of the proton and electron ii) ground state : lowest energy state iii) excited state : higher energy levels iv) energy of photon = energy difference between two levels 1) Bohr Model (cont.) 전자 1 개가 n = 3 에서 n = 2 로이동할때 : E 3 = J ; E 2 = J E hi - E lo = J λ = hc E E photon = E = E hi - E lo

3 2) Quantum Mechanical Model 6.3 Quantum Numbers 특정한지역에서전자를발견할확률에대해서만언급할수있음 전자의운동에너지는 ( 전자가움직이는 ) 부피에반비례한다. 한원자의전자가가진에너지를정확하게기술하기위해서는 4 가지양자수가필요하다. n : principal quantum number l : angular momentum quantum number m l : magnetic quantum number m s ; spin quantum number 1) First Quantum Number, n; Principal Energy Levels n = 1, 2, 3,... n 값은전자의에너지와핵으로부터의거리를결정하는주된인자이다. maximum capacity of principal level = 2n 2 n Max no. of e - 2) Second Quantum Number, l; Sublevels (s, p, d, f ) l = 0, 1, 2...(n-1) n =1 l = n =2 l = n =3 l = In general, number of sublevels = n.

4 Sublevel Designations Sublevels designated as: s, p, d, f Value of l ) Third Quantum Number, m l ; Orbitals m l = l, l 1, 1, 0, -1,.- l 궤도함수의모양, 방향 Letter s p d f Capacity order of energy ns np nd nf s p d f 0 (one s orbital) 4) Fourth Quantum Numer, m s ; Electron Spin 6.4 Atomic Orbitals: Shapes and Sizes 한궤도함수에속한전자는두개의스핀중하나를가진다 : m s = +1/2, 1/2 5) Pauli Exclusion Principle No two electrons in an atom can have the same set of four quantum number No more than two electrons can occupy each orbital. Two electrons must have opposed spins. Orbital names n l m l Orbital s 궤도함수는핵을중심으로한구형이다. p 궤도함수는아령모양이며, p 궤도함수각각은서로 90 각도로이루어져있다.(p x, p y, p z orbitals)

5 6.5 Electron Configurations in Atoms Electron configuration : an expression giving the population of electrons in each sublevel (superscript) 1s 2 2s 2 2p 1 Sublevels in order of increasing energy 1) Electron Configuration from Sublevel Energies H: 1s Li: [He]2s Na:[Ne]3s K: [Ar]4s He:1s Be:[He]2s Mg:[Ne]3s Ca:[Ar]4s B: [He]2s 2p Al: [Ne]3s 3p Sc: [Ar]4s 3d Ne:[He]2s 2p Ar:[Ne]3s 3p Zn: [Ar]4s 3d Kr: [Ar]4s 3d 4p 2) Filling of Sublevels and the Periodic Table Beyond krypton, it s best to derive electronic configurations from the periodic table. 1 Groups 1, 2: 2 Groups 13-18: 3 Groups 3-12: 4 Lanthanides and actinides: 6.6 Orbital Diagrams of Atoms ( 원자의궤도함수도표 ) 각궤도함수에있는전자의수와전자의스핀을표시함. 1s 2s 2p H ( ) He ( ) Li ( ) ( ) Be ( ) ( ) B ( ) ( ) ( ) ( ) ( ) C ( ) ( ) ( ) ( ) ( ) Ν ( ) ( ) ( ) ( ) ( ) Ο ( ) ( ) ( ) ( ) ( )

6 6.6 Orbital Diagrams of Atoms (cont.) 6.7 Electron Configuration in Monatomic Ions ex) What is the abbreviated electron configuration and orbital diagram of Fe? [Ar]4s 3d 4s 3d [Ar] ( ) ( )( )( )( ) ( ) 1) Ions with noble gas structures (Groups 1, 2, 16, 17) 1 비금속워소들 ; 전자를얻어외곽에 8개가되도록함 2 금속원자들 ; 전자를잃어외곽에 8개가되도록함 2) Transition Metal Cations 전이금속양이온 ; 외곽의 s 전자를먼저잃음 : 24Cr 3+ [Ar]3d 3 27Co 2+ [Ar]3d 7 30Zn 2+ [Ar]3d Periodic Trends in the Properties of Atoms The chemical and physical properties of elements are a periodic function of atomic number 2) Ionic Radius Trends parallel those in atomic radius. Beyond that: 1) Atomic radius In general, atomic radius decreases going across a period from left to right, increases going down a group. cations are anions are than corresponding atoms than corresponding atoms Trends can be explained in terms of effective nuclear charge felt by outer electron(s). This means that, in a typical ionic compound, the anions occupy most of the space. Electrons in outer levels do not shield one another effectively.

7 3) Ionization Energy ( 이온화에너지 ) 4) Electronegativity ( 전기음성도 ) Energy that must be absorbed to convert an atom to a +1 ion. Na(g) Na + (g) + e - I.E. = +496 kj/mol going across in periodic table, as atoms get smaller going down in periodic table, as atoms get larger A property of an atom that increases with its tendency to attract electrons to a covalent bond. going across in periodic table going down in periodic table