Modern Atomic Model and EMR. Describe the electromagnetic spectrum in terms of frequency,...
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Transcript of Modern Atomic Model and EMR. Describe the electromagnetic spectrum in terms of frequency,...
Modern Atomic Model and EMR
• Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy.
Include: quantum, photon • Understand how unique line spectra are
created for each element.Additional KEY Terms
Spectroscopy EmissionLine spectrum
Maxwell (1860) - all energy radiated from objects (including visible light) is electromagnetic radiation.
Composed of radiated waves of both electrical and magnetic energy
Wavelength and frequency are inversely related
Wavelength (λ - “lambda”): distance from point to the same point on the next wave.
Frequency (ν – “nu” or ƒ): number of wavelengths, or cycles, that pass a point per unit time.
Frequency measured in cycles per second (s-1), or the SI unit hertz (Hz)
Amplitude: height of the wave from origin to crest.
Wavelength and frequency do not affect amplitude
Types of Electromagnetic radiation
f and λ determine what you see or feel, amplitude determines how bright or hot
Memorize this wavelength
range…
Sunlight (white light) shone through a prism separates it into a continuous spectrum of colours.
The different wavelength for each colour causes them to refract or bend at different anglesIt will always be - ROY G BIV
All EMR radiates at 3.00 x 108 m/s in a vacuum.
This universal value (c) is a product of the wavelength and frequency of the radiated energy.
“speed of light”
c = λν
c = λƒ
The colours seen in fireworks are a result of burning different salts. Red light has a wavelength of 650 nanometres. Calculate the frequency of red light (1 nm - 1.0 x 10-9 m).
ƒλc =
ƒ 650 x 10-9 m
= 3.00 x 108 m/s
ƒ = 4.6 x 1014 Hz
Colour Elementgreen copper
yellow sodium
red strontium
yellow-green
barium
orange-red calciumpurple potassium
purple-red lithium
• Burning small amounts of each element gave off a unique colour of light
• Used to detect a metals presence
Planck (1900)
Focusing this light through a prism also produces a spectrum, but
ONLY distinct lines appear
Investigated heating objects and
Energy emitted by a element can be separated – to produce a Line spectrum
(emission spectrum) Disclaimer: This is not as simple as my “art” looks
The colored lines of the atoms (or Spectral Lines) are a kind of "signature" for the atoms.
C
O
Spectroscopy and spectrophotometry are techniques used to investigated EMR emissions.
Planck's Radiation Law: Energy is transmitted in discrete amounts – called quanta.
EMR is a stream of tiny “packets” of quantized energy carried by particle-like photons.
A photon has no mass but carries a quantum
of energy
Eq = hfE – energy of a quantum (Joules) h – Plank’s constant (6.626 x 10-34 J s)f – frequency of absorbed or emitted EMR
Energy (quantum) contained in a photon is directly related to the frequency of the radiation.
So higher frequency waves contained larger “packets” of
energy
The blue colour of fireworks is often achieved by heating copper (I) chloride to about 1200oC. The wavelength of the blue light is 450 nm. What is the quantum of energy emitted by this light?
E = hf
ƒ = c λ
ƒ 450 x 10-9 m
= 3.00 x 108 m/s
ƒ = 6.7 x 1014 Hz
E = (6.626 x 10-34J· s)(6.7 x 1014 Hz)
E = 4.4 x 10-19Jq
CAN YOU / HAVE YOU?• Describe the electromagnetic spectrum in
terms of frequency, wavelength, and energy.
Include: quantum, photon
• Understand how unique line spectra are created for each element.
Additional KEY TermsSpectroscopy EmissionLine spectrum