Modern Atomic Model and EMR

Understand how line spectra are created. Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy. Understand how line spectra are created. Additional KEY Terms Spectroscopy Emission Quantum Line spectrum

Composed of radiated waves of both electrical and magnetic energy Maxwell (1860) - all energy radiated from objects (including visible light) is electromagnetic radiation. Composed of radiated waves of both electrical and magnetic energy

Amplitude: height of the wave from origin to crest. 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 Wavelength and frequency are inversely related

Types of Electromagnetic radiation f and λ determine what you see or feel, amplitude determines how bright or hot

c = λƒ c = λν 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 = λƒ c = λν

It will always be - ROY G BIV 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 angles It will always be - ROY G BIV

Investigated heated objects and Planck (1900) Investigated heated objects and Burning small amounts of each element gave off a unique colour of light Used to detect a metals presence Colour Element green copper yellow sodium red strontium yellow-green barium orange-red calcium purple potassium purple-red lithium Focusing this light through a prism also produces a spectrum, but ONLY distinct lines appear

Disclaimer: This is not as simple as my drawing looks Energy emitted by a element can be separated – to produce a Line spectrum (emission spectrum) Disclaimer: This is not as simple as my drawing looks

The colored lines of the atoms (or Spectral Lines) are a kind of "signature" for the atoms. Spectroscopy and spectrophotometry are techniques used to investigated EMR emissions. C O

Quantum is the smallest “packet” of energy gained or lost by an atom. Planck's radiation law: Equation that accounted for light from heated objects, BUT it needed energy to be gained or lost in discrete amounts – called quanta. Quantum is the smallest “packet” of energy gained or lost by an atom. Planck couldn’t explain WHY energy had to be “quantized,” but it worked and predicted experimental values

So higher frequency waves contained larger “packets” of energy Energy contained in a quantum was directly related to the frequency of radiation emitted. Eq = hf E – energy of a quantum (Joules) h – Plank’s constant (6.626 x 10-34 J s) f – frequency of absorbed or emitted EMR So higher frequency waves contained larger “packets” of energy

Understand how line spectra are created. CAN YOU / HAVE YOU? Describe the electromagnetic spectrum in terms of frequency, wavelength, and energy. Understand how line spectra are created. Additional KEY Terms Spectroscopy Emission Quantum Line spectrum