C. Johannesson

III. Quantum Model

of the Atom(p. 98 - 104)

Ch. 4 - Electrons in Atoms

C. Johannesson

A. Electrons as WavesLouis de Broglie (1924)

Applied wave-particle theory to e-

e- exhibit wave properties

QUANTIZED WAVELENGTHS

C. Johannesson

A. Electrons as WavesQUANTIZED WAVELENGTHS

C. Johannesson

A. Electrons as Waves

EVIDENCE: DIFFRACTION PATTERNS

ELECTRONSVISIBLE LIGHT

C. Johannesson

B. Quantum MechanicsHeisenberg Uncertainty Principle

Impossible to know both the velocity and position of an electron at the same time

C. Johannesson

B. Quantum Mechanics

σ3/2 Zπ

11s 0

eΨ a

Schrödinger Wave Equation (1926) finite # of solutions quantized energy

levels defines probability of finding an e-

C. Johannesson

B. Quantum Mechanics

Radial Distribution CurveOrbital

Orbital (“electron cloud”) Region in space where there is 90%

probability of finding an e-

C. Johannesson

C. Quantum Numbers

UPPER LEVEL

Four Quantum Numbers: Specify the “address” of each electron in

an atom

C. Johannesson

C. Quantum Numbers

1. Principal Quantum Number ( n )

Energy level

Size of the orbital

n2 = # of orbitals in the energy level

C. Johannesson

C. Quantum Numbers

s p d f

2. Angular Momentum Quantum # ( l ) Energy sublevel Shape of the orbital

C. Johannesson

C. Quantum Numbers

n = # of sublevels per leveln2 = # of orbitals per levelSublevel sets: 1 s, 3 p, 5 d, 7 f

C. Johannesson

C. Quantum Numbers

3. Magnetic Quantum Number ( ml ) Orientation of orbital Specifies the exact orbital

within each sublevel

C. Johannesson

C. Quantum Numbers

px py pz

C. Johannesson

C. Quantum Numbers

Orbitals combine to form a spherical shape.

2s

2pz2py

2px

C. Johannesson

C. Quantum Numbers

4. Spin Quantum Number ( ms ) Electron spin +½ or -½ An orbital can hold 2 electrons that spin

in opposite directions.

C. Johannesson

C. Quantum Numbers

1. Principal # 2. Ang. Mom. # 3. Magnetic # 4. Spin #

energy levelsublevel (s,p,d,f)orbitalelectron

Pauli Exclusion Principle No two electrons in an atom can have

the same 4 quantum numbers. Each e- has a unique “address”:

C. Johannesson

Feeling overwhelmed?

Read Section 4-2!