Light and the electron Quest continues to discover the structure of atom and how electrons are arranged within atoms.

Wave Nature of Light Electromagnetic radiation – form of energy exhibiting wave-like behavior Ex. Visible light

Wavelength (λ) Distance between adjacent peaks in a wave. Measured in meters.

Speed of light (c) Light travels at 186,000 mi/s 3.00 x 108 m/s c = 3.00 x 108 m/s

Frequency (Ʋ) Number of peaks which pass a point per second. Ʋ = 1/s (Hz)

Wavelength vs. Frequency

Putting it together c = λƲ 3.00 x 108 m/s = λƲ Pg. 121 practice problems 1-4

Electromagetic radiation (light) To microwave

Particle Nature of Light Wave nature of light didn’t explain many important aspects – Why heated objects emit only certain frequencies of light at given temp.? Quantum concept – heated objects emitting different frequencies of light. Energy emitted corresponds to certain Ʋ & λ Quantum- minimum amount of energy that can be gained or lost by an atom

Max Planck Energy of quantum is related to the frequency of the emitted radiation Equantum = hƲ E = energy Ʋ = ? h (Planck’s constant) = 6.626 x 10–34 J · s Greater the frequency, greater the energy – directly proportional Pg. 124 practice problems 5,6

Atomic Emission Spectra – light produced in glowing neon signs Pass energy through tube filled with gas Causes electrons to absorb energy & become excited As unstable, excited electrons lose energy and spiral towards the nucleus they give off energy that corresponds with certain frequencies of light When emitted light is passed through a prism→ atomic emission spectra Each atom’s atomic emission spectrum is unique and can be used to determine if that element is part of an unknown compound. Pg. 126

Bohr e-

Bohr e-

Bohr e-

Bohr e-

Bohr e-

Hydrogen spectrum