BIG topics... Light (electromagnetic radiation)

particle/wave dual nature of light c, λ, ט , E & h

Quantum theory (wave mechanical model) Bohr model of Hydrogen atom absorption/emission quantum numbers & orbital shapes

Electron configurations orbital, e- configuration noble gas notation Aufbau, Pauli & Hund

WavesWaves Wavelength () - length of one

complete wave. Common units: m or nm

Frequency () - # of waves that pass a point during a certain time periodCommon Units: hertz (Hz) = 1/s = s-1

Amplitude (A) - distance from the origin to the trough or crest

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Wavelength and FrequencyWavelength and Frequency

E = h

c = c = speed of light (3.0 x 108 m/s) = frequency (s-1)= wavelength (m)

E = energy (Joules or J)h= Planck’s constant (6.626 x10-34 J s) = frequency (s-1)

“nu” “lamda”

Highest energy

Moderate energy

Lowest energy

Visible part of EM SPectrumVisible part of EM SPectrum

PRISM

Slit

Ray of

White Light

Waves 1/33,000” long

Waves 1/70,000” long

RedOrangeYellowGreenBlueIndigoViolet

400 nm – 700 nm

Electromagnetic SpectrumElectromagnetic Spectrum

GIVEN:

h x 10-34 J s

c = 3.00 x 108 m/s

= ?

= 1.0 x 10-3 nm = ???? m

WORK: = c = 3.00 108 m/s 1.0 x 10-12 m = 3.0 x 1020 s-1

Find the energy of a photon with a Find the energy of a photon with a wavelength of 1.00 x 10wavelength of 1.00 x 10-3-3 nm. nm.

E = hvc = λv

= (6.626 x 10-34 J s)(3.0 x 1020s-1)

E = 1.99 x 10-13 J

E = hc λ

Quantum TheoryQuantum Theory

Max Planck Max Planck (1900)(1900)

ObservedObserved - emission of light from hot - emission of light from hot objectsobjects

ConcludedConcluded - energy is - energy is emitted in small, specific emitted in small, specific amounts (quanta)amounts (quanta)

QuantumQuantum - minimum amount of energy - minimum amount of energy gained or lost by an atomgained or lost by an atom

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Continuous vs. Quantized Continuous vs. Quantized EnergyEnergy

Ene

rgy

A Bcontinuous quantized

Acontinuous

Bquantized

Bohr Model of Bohr Model of HydrogenHydrogen

Nucleus

Possible electron orbits

eGreat theory, BUT it turned out to be totally wrong!! Next week we’ll see a better theory

Further away from nucleus means higher energy level…

Excitation of Hydrogen Atoms

Return to Ground State

Emission Spectrum of Hydrogen

1 nm = 1 x 10-9 m = “a billionth of a meter”

410 nm 434 nm 486 nm 656 nm

Continuous and Line Spectra

light

Na

H

Ca

Hg

400 450 500 550 600 650 700 750 nm

Visiblespectrum

(nm)

An Excited Lithium Atom

Photon ofred lightemitted

Li atom inlower energy state

Excited Li atom

Ene

rgy

Preview....Orbital ShapesPreview....Orbital Shapes