Atomic Structure and Periodicity Electromagnetic Radiation and Nature of Matter

Atomic Structure and Atomic Structure and PeriodicityPeriodicity

Electromagnetic Radiation and Electromagnetic Radiation and Nature of MatterNature of Matter

Quantum TheoryQuantum Theory

From Democritus to From Democritus to Einstein has come the Einstein has come the modern atomic modern atomic theory.theory.

What is the nature of What is the nature of atoms? Remember atoms? Remember Dalton’s theory?Dalton’s theory?

Electromagnetic RadiationElectromagnetic Radiation

One way energy One way energy travel through space travel through space is via electromagnetic is via electromagnetic radiation.radiation.

All forms of radiant All forms of radiant energy have wavelike energy have wavelike behavior.behavior.

WavesWaves

Waves have 3 Waves have 3 characteristics:characteristics:WavelengthWavelengthFrequencyFrequencySpeedSpeed

Wave characteristicsWave characteristics

is the symbol for wavelength, the is the symbol for wavelength, the distance between two consecutive peaks.distance between two consecutive peaks.

isis the frequency and is number of the frequency and is number of waves that pass through a given point in waves that pass through a given point in space in 1 second.space in 1 second.

The speed of all electromagnetic radiation The speed of all electromagnetic radiation is the speed of light or c.is the speed of light or c.

Wavelength and FrequencyWavelength and Frequency

The longer the The longer the wavelength, the wavelength, the shorter the shorter the frequency.frequency.

= c= cUnits for Units for are are

1/sec or hertz, Hz.1/sec or hertz, Hz.

Waves have energy!Waves have energy!

Microwaves passing through water Microwaves passing through water transfer their energy to the water and transfer their energy to the water and eventually heating the water to eventually heating the water to boiling.boiling.

Fire transfers heat by infrared Fire transfers heat by infrared radiation.radiation.

Which is higher energy? Red or blue Which is higher energy? Red or blue light?light?

Flame tests!Flame tests!

Example:Example:Sr(NOSr(NO33))22 gives gives

off a red flame of off a red flame of 650 nm. 650 nm.

What is its What is its frequency?frequency?

AnswerAnswer

= c or = c or = c/ = c/ = 6.50 nm x 10= 6.50 nm x 1022

C = 2.9979 x 10C = 2.9979 x 1088 m/s m/s1 m = 1 x 101 m = 1 x 1099 nm nm = 4.61 x 10= 4.61 x 101414 Hz Hz

Nature of MatterNature of Matter

1919thth century thought: Matter and energy century thought: Matter and energy are distinct.are distinct.

Matter was made of particles.Matter was made of particles.Light was an energy that moved in waves.Light was an energy that moved in waves.With that the study of physics was With that the study of physics was

complete, there would be no new complete, there would be no new information, or was there?information, or was there?

Max PlanckMax PlanckStudied radiation of soft bodies Studied radiation of soft bodies

heated to incandescence. (light)heated to incandescence. (light)Originally thought matter could Originally thought matter could

absorb or emit any quantity of absorb or emit any quantity of energy.energy.

Max found that the energy could Max found that the energy could only be gained or lost in whole only be gained or lost in whole number multipliers of the number multipliers of the equationequation hh

Planck’s ConstantPlanck’s Constant

h is Planck’s constant and was found to h is Planck’s constant and was found to equal 6.626 x 10equal 6.626 x 10-34-34 J Js.s.

The change in energy for a system may The change in energy for a system may be found by be found by ΔΔE=nhE=nh

This equation states that energy is This equation states that energy is given off in packets or quantized.given off in packets or quantized.

Each packet of energy is a quantum.Each packet of energy is a quantum.

ExampleExample

The blue in fireworks is often The blue in fireworks is often from Copper (I) chloride heated from Copper (I) chloride heated to 1200to 1200°C. Blue light has a °C. Blue light has a wavelength of 450 nm. What is wavelength of 450 nm. What is the quantum of energy that may the quantum of energy that may be emitted by light at 450 nm?be emitted by light at 450 nm?

AnswerAnswer

ΔΔE=nhE=nh n=1n=1 = c/= c/==2.9979 x 102.9979 x 1088 m/s m/s 4.5 x 104.5 x 10-7-7 m m

=6.6x10=6.6x10 14 14 s s-1-1