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Chapter 4 Arrangement of Electrons in Atoms

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I. The Development of a New Atomic Model H Electromagnetic Radiation: H Electromagnetic Spectrum: H Electromagnetic Radiation: H Electromagnetic Spectrum:

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H Wavelength ( ): corresponding points on adjacent waves---Ex: Frequency ( ): # of waves that pass a point in a specific time H c = ( ) ( ) ------inversely proportional H Wavelength ( ): corresponding points on adjacent waves---Ex: Frequency ( ): # of waves that pass a point in a specific time H c = ( ) ( ) ------inversely proportional

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c : m/s : m, cm, nm : waves/second--Hertz (Hz) H c = ( ) ( ) ------inversely proportional c : m/s : m, cm, nm : waves/second--Hertz (Hz)

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H Photoelectric Effect: emission of e- by certain metals when light shines on them

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H Quantum: min quantity of nrg that can be lost or gained by an atom H E = (h) ( ) o J = (J s) (Hz) o Planck’s constant: 6.626 X 10 -34 J s H Quantum: min quantity of nrg that can be lost or gained by an atom H E = (h) ( ) o J = (J s) (Hz) o Planck’s constant: 6.626 X 10 -34 J s

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Einstein o dual wave-particle to describe light H Photon: radiation with zero mass carrying a quantum of nrg o packet of nrg emitted when an e- drops nrg levels Einstein o dual wave-particle to describe light H Photon: radiation with zero mass carrying a quantum of nrg o packet of nrg emitted when an e- drops nrg levels

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H Ground state: lowest nrg state H Excited state: higher potential nrg H Ground state: lowest nrg state H Excited state: higher potential nrg

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--Bohr’s Model-- G e - exist only in orbits with specific amounts of energy called energy levels G Therefore… G e - can only gain or lose certain amounts of energy G only certain photons are produced G e - exist only in orbits with specific amounts of energy called energy levels G Therefore… G e - can only gain or lose certain amounts of energy G only certain photons are produced

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Line-Emission Spectrum ground state excited state ENERGY IN PHOTON OUT

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Bohr Model 1 2 3 4 5 6 -Energy of photon depends on the difference in energy levels -Bohr’s calculated energies matched the IR, visible, and UV lines for the H atom

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Other Elements G Each element has a unique bright-line emission spectrum. G “Atomic Fingerprint” Helium zBohr’s calculations only worked for hydrogen! ----pg 97

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II. The Quantum Model of the Atom G A. Electrons as Waves o Diffraction: bending of a wave as it passes by the edge of an object o Interference: results when waves overlap G A. Electrons as Waves o Diffraction: bending of a wave as it passes by the edge of an object o Interference: results when waves overlap

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EVIDENCE: DIFFRACTION PATTERNS VISIBLE LIGHT ELECTRONS

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zHeisenberg Uncertainty Principle yImpossible to know both the velocity and position of an electron at the same time

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G Schrödinger Wave Equation (1926) G finite # of solutions quantized energy levels G defines probability of finding an e - G Schrödinger Wave Equation (1926) G finite # of solutions quantized energy levels G defines probability of finding an e -

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A. Atomic Orbitals and Quantum Numbers G Orbital: probable location of an e- G Quantum #: properties of atomic orbitals and properties of e-’s in orbitals G Principal quantum #: (n), indicates main nrg level occupied by the e- o n = 1 -----occupies 1st nrg level G Orbital: probable location of an e- G Quantum #: properties of atomic orbitals and properties of e-’s in orbitals G Principal quantum #: (n), indicates main nrg level occupied by the e- o n = 1 -----occupies 1st nrg level

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G Angular momentum quantum #: (l), indicates shape of orbital G Magnetic quantum #: (m), orientation of an orbital G Spin quantum #: which spin state (+)(-) G ***See table 4-2 pg 104 G Angular momentum quantum #: (l), indicates shape of orbital G Magnetic quantum #: (m), orientation of an orbital G Spin quantum #: which spin state (+)(-) G ***See table 4-2 pg 104

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zOrbital (“electron cloud”) yRegion in space where there is 90% probability of finding an e - Orbital Radial Distribution Curve

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zFour Quantum Numbers: ySpecify the “address” of each electron in an atom UPPER LEVEL

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1. Principal Quantum Number ( n ) yEnergy level ySize of the orbital yn 2 = # of orbitals in the energy level

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2. Angular Momentum Quantum # ( l ) yEnergy sublevel yShape of the orbital s p d f

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zn=# of sublevels per level zn 2 =# of orbitals per level zSublevel sets: 1 s, 3 p, 5 d, 7 f

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3. Magnetic Quantum Number ( m l ) yOrientation of orbital Specifies the exact orbital within each sublevel

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4. Spin Quantum Number ( m s ) yElectron spin +½ or -½ yAn orbital can hold 2 electrons that spin in opposite directions.

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III. Electron Configuration G Aufbau principle: lowest nrg orbits fill first G Pauli exclusion principle: no 2 e-’s can have the same 4 quantum #’s. This is where spin allows 2 e-’s to be in the same orbit o Ex: G Aufbau principle: lowest nrg orbits fill first G Pauli exclusion principle: no 2 e-’s can have the same 4 quantum #’s. This is where spin allows 2 e-’s to be in the same orbit o Ex:

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G Hund’s rule: orbital of equal nrg are occupied by 1 e-, before any is occupied by 2 e-’s o Ex: G Orbital Notation: ex: pg 107 G Electron Config Notation: pg 107 G Electron Dot diagram: ex G Hund’s rule: orbital of equal nrg are occupied by 1 e-, before any is occupied by 2 e-’s o Ex: G Orbital Notation: ex: pg 107 G Electron Config Notation: pg 107 G Electron Dot diagram: ex

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G Noble gases: G are inert G complete octet G --show ex---- G Noble gases: G are inert G complete octet G --show ex----

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G Table 4-3 pg 110 1. Principal # energy level 2. Ang. Mom. # sublevel (s,p,d,f) 3. Magnetic # orbital 4. Spin # electron G Table 4-3 pg 110 1. Principal # energy level 2. Ang. Mom. # sublevel (s,p,d,f) 3. Magnetic # orbital 4. Spin # electron

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