III. Quantum Model of the Atom Ch. 6 - Electrons in Atoms

A. Electrons as Waves zLouis de Broglie (1924) yApplied wave-particle theory to e - ye - exhibit wave properties QUANTIZED WAVELENGTHS

A. Electrons as Waves QUANTIZED WAVELENGTHS

B. Quantum Mechanics zHeisenberg Uncertainty Principle yImpossible to know both the velocity and position of an electron

B. Quantum Mechanics zSchrödinger Wave Equation (1926) yfinite # of solutions  quantized energy levels ydefines probability of finding an e -

B. Quantum Mechanics z Schrodinger wave equation and Heisenberg Uncertainty Principle laid foundation for modern quantum theory zQuantum theory: (def) describes mathematically the wave properties of e- and other very small particles

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

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

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

C. Quantum Numbers s p d f 2. Angular Momentum Quantum # ( l ) yEnergy sublevel yShape of the orbital (# of possible shapes equal to n) y values from 0 to n-1

C. Quantum Numbers If l equals…Then orbital shape is… 0s 1p 2d 3f Principle quantum # followed by letter of sublevel designates an atomic orbital

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

C. Quantum Numbers z Values for m l : m = - l … 0… + l

C. Quantum Numbers pxpx pypy pzpz

zOrbitals combine to form a spherical shape. 2s 2p z 2p y 2p x

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

C. Quantum Numbers 1. Principal #  2. Ang. Mom. #  3. Magnetic #  4. Spin #  energy level sublevel (s,p,d,f) orbital electron zPauli Exclusion Principle yNo two electrons in an atom can have the same 4 quantum numbers. yEach e - has a unique “address”:

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

Wrap-Up Quantum #SymbolWhat it describes Possible values Principle quantum # n main E level, size of orbital n = positive whole integers Angular Momentum Quantum # l sublevels and their shapes 0 to (n-1) Magnetic Quantum # m l orientation of orbital - l … 0 … + l Spin Quantum # m s electron spin+1/2 or -1/2

Feeling overwhelmed? Read Section 6-5!