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Modern Atomic Theory Electrons in the Atom Electromagnetic Spectrum. Fundamentals of Light. Neon advertising signs are formed from glass tubes bent in various shapes. An electric current passing through the gas in glass tube makes the gas glow with its own characteristic color.

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Modern atomic theory electrons in the atom electromagnetic spectrum
Modern Atomic TheoryElectrons in the AtomElectromagnetic Spectrum

  • Neon advertising signs are formed from glass tubes bent in various shapes.

  • An electric current passing through the gas in glass tube makes the gas glow with its own characteristic color.

  • Why does each gas glow with a specific color of light?

Light the ground state is the lowest energy level that an electron can occupy


The ground state is the lowest energy level that an electron can occupy.

The excited state is a higher energy level that an electron may move to after absorbing energy

The excited state is a higher energy level that an electron may move to after absorbing energy.

The amount of energy absorbed by the electron is equal to the energy of the photon which is emitted

The amount of energyabsorbed by the electron is equal to the energy of the photon which is emitted.

A quantum leapis the jump in energy level that an electron will make after absorbingthe correct quanta of energy.

A quantum is a packet of energy that electrons absorb to change energy levels.

Light (photons): form of some of the electromagnetic radiation (energy) released by electrons as theyreturnto their ground state from their excited state.

Energy absorbed


see light

  • Energy  increases

  • Ground state  excited state

    (where electrons are suppose to be)

    Sun gives tremendous amount of energy (ground  excited)

Electromagnetic radiation

  • All electrons are sitting in ground state

  • Turn on light  electricity

    (goes to a higher e- level)

  • If electricity still on  out

  • Little burst of energy

Lights off  Ground state

Lights on  excited state

(always little bursts of energy going on)

Excited gases atomic structure
Excited Gases & Atomic Structure

Electromagnetic radiationis a form of energy that exhibitswavelikebehavior as it travels through space.

Electromagnetic radiation2
Electromagnetic Radiation

  • Most subatomic particles behave as PARTICLES and obey the physics of waves.


  • Wavelength () –(Greek letter lambda), length of one complete wave (distance between crests)

  • Frequency () – (Greek letter nu) # of waves that pass a point during a certain time period

    • hertz (Hz) = 1/s

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








greater amplitude


greater frequency


Electromagnetic radiation3


Visible light




Ultaviolet radiation

Electromagnetic Radiation


  • The wavelength and frequency of light are inversely proportional to each other.

Low energy

High Energy


  • Sunlight consists of light with a continuous range of wavelengths& frequencies.

  • The electromagnetic spectrum consists of radiation over a broad band of wavelengths.

Electro magnetic spectrum

In increasing energy, ROYGBIV

Electromagnetic spectrum

increasing frequency

increasing wavelength

Electromagnetic Spectrum

Long wavelength --> small frequency (low energy)

Short wavelength --> high frequency (High energy)

Types of em radiation
Types of EM Radiation

  • Radiowaves

    • lowest energy EM radiation

    • Receives in radio ( unscrables)

Types of em radiation1
Types of EM Radiation

  • Radar

    • Military, space, sonar, weather

    • Speeding (cops)

  • Microwaves

    • penetrate food and vibrate water & fat molecules to produce thermal energy

    • Telephone & cell phone signals

Types of em radiation2
Types of EM Radiation

  • Infrared Radiation (IR)

    Used by military ( to see in drk)

    • slightly lower energy than visible light

    • can raise the thermal energy of objects

    • thermogram - image made by detecting IR radiation

Infrared measures heat
Infrared Measures Heat

Every object with a temperature above absolute zero radiates in the infrared.

Infrared in society
Infrared in Society

  • Oceanography

  • Firefighting

  • Commercial Applications

Types of em radiation3















Types of EM Radiation

  • Visible Light

    • small part of the spectrum we can see

    • ROY G. BIV - colors in order of increasing energy

How to split light
How to split Light:

a) Prism (curve each wave length)

B mirror water wavelength of light
B) Mirror & Water  wavelength of light

A spectroscope: device used to view the visible wavelengths of light produced by different atoms.

The wavelengths are visible as bright lineson the spectrum.

Types of em radiation4
Types of EM Radiation

  • Ultraviolet Radiation (UV)

    • slightly higher energy than visible light

    • Types:

      • UVA - tanning, wrinkles

      • UVB - sunburn, cancer

      • UVC - most harmful, sterilization

Bumble bee

Insects can see uv waves

Types of em radiation5
Types of EM Radiation

  • Ultraviolet Radiation (UV)

    • Ozone layer depletion = UV exposure!

Types of em radiation6
Types of EM Radiation

  • X rays

    • higher energy than UV

    • can penetrate soft tissue, but not bones

    • Put a lead vest over body

Types of em radiation7

Radiation treatment using radioactive cobalt-60.

Types of EM Radiation

  • Gamma rays

    • highest energy EM radiation

    • emitted by radioactive atoms

    • used to kill cancerous cells

The particular wavelength of light produced is specific for each element and can be used to identify it.

Line emission spectra of excited atoms
Line Emission Spectra of Excited Atoms

  • Excited atoms emit light of only certain wavelengths

  • The wavelengths of emitted light depend on the element.

Spectrum of excited hydrogen gas
Spectrum of Excited Hydrogen Gas

Light spectrum

Slit that allows light inside

Light Spectrum

Line up the slit so that it is parallel with the spectrum tube (light bulb)


A flame test : method used to identify and element by the color of flame it produces.

Ex: copper produces

a characteristic

green flame.

Fingerprints of light example conclusion
Fingerprints of Light Example conclusion

  • During this experiment, several different metal ions emit a distinct color when held into a flame . Because each metal emitted a different color, the metal cation can be identified. In this experiment, Barium, copper, strontium, potassium, lithium, and sodium, were identified. Colors were yellow-green, green, red, violet, red-orange, & orange.

  • Important concepts involved in this lab include atomic orbitals, the energy states of atoms, ions, and atomic emission. Electrons orbit the nucleus in “shells”, each shell has a principle quantum number. Each electron has a ground stage but when it acquires energy it becomes “excited” and gains a higher principle quantum number. The emission spectra, or how it is seen with light, is obtained by adding energy and then having the electrons fall to the ground ( excited state)

  • Thus, identification of elements can be done because of the different colors that are given off by the jumping electrons.

  • SOURCES OF ERRORS: different flame/gas levels, contaminated solutions, different ions held in flame different lengths of time, color blindness

The electric pickle
The Electric Pickle

  • Excited atoms can emit light.

  • Here the solution in a pickle is excited electrically.

  • The Na+ ions in the pickle juice give off light characteristic of that element.


  • Light

    • How are the wavelength and frequencyof light related?

Electromagnetic radiation4
Electromagnetic Radiation

  • Waves have a frequency

  • Use the Greek letter “nu”, , for frequency, and units are “cycles per sec”

  • All radiation:  •  = c

  • where c = velocity of light = 3.00 x 108m/sec

Em spectrum
EM Spectrum

  • Frequency & wavelength are inversely proportional

c = 

c: speed of light (3.00  108 m/s)

: wavelength (m, nm, etc.)

: frequency (Hz)

Em spectrum1


 = c

 = 3.00  108 m/s

4.34  10-7 m

EM Spectrum

  • EX: Find the frequency of a photon with a wavelength of 434 nm.


 = ?

 = 434 nm = 4.34  10-7 m

c = 3.00  108 m/s

= 6.91  1014 Hz


  • According to the wave model, light consists of electromagnetic waves.

    • Electromagnetic radiationincludes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays.

    • All electromagnetic waves travel in a vacuum at a speed of 2.998  108 m/s.

Quantum theory
Quantum Theory

  • The energy of a photon (light quanta) is proportional to its frequency. (E = h x v)

E: energy (J, joules)

h: Planck’s constant (6.6262  10-34 J·s)

: frequency (Hz)

E = h

Quantum theory1
Quantum Theory

  • EX: Find the energy of a red photon with a frequency of 4.57  1014 Hz.

  • E = H x V


E = ?

 = 4.57  1014 Hz

h =6.6262  10-34 J·s


E = h

E = (6.6262  10-34 J·s) (4.57  1014 Hz)

E = 3.03  10-19 J