the arrangement of electrons in atoms the development of the new atomic model
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The Arrangement of Electrons in Atoms
The Development of the New Atomic Model
The Dual Nature of Light
• Before 1900, scientists thought light behaved solely as a wave.
• We now know that light has particle-like characteristics as well.
• Some properties are best explained by light’s wave nature others by it’s particle nature.
Electromagnetic Radiation
• Includes visible light, x-rays, ultraviolet, infrared light, microwaves and radio waves.
• Exhibits wave like behavior.• Is related to _________ and __________.
What does the name suggest?
Electromagnetic Spectrum
Wave Diagram
Wave Characteristics
• Wavelength- The distance between two consecutive peaks or troughs.
• Frequency- The number of waves that pass a point each second (the unit is the Hertz, Hz). One complete wave or cycle per. second = 1 Hz.
• Velocity- Distance a peak moves in a unit of time.
c = f • velocity = frequency x wavelength• The speed (velocity) of electromagnetic waves is
constant (c).C = 3.0 x 108m/s
• If you know the frequency you can calculate the wavelength and…
• SO WHAT DOES ALL THIS HAVE TO WITH A NEW ATOMIC MODEL??
We are getting to that…It will take some time though.
It took the best minds in science years to explain …it should take us at least a few classes…so do not worry if it does not come easy.
Why do we need to learn about this???
• An understanding of the arrangement of electrons makes it possible to explain/predict the chemistry of the elements…in other words, it will make the rest of the course much easier…
• The more you understand about what things are made of including yourself, the universe and everything in it the more you will appreciate it.
• SO…
c = f• velocity = frequency x wavelength• The speed (velocity) of electromagnetic
waves is constant (c).C = 3.0 x 108m/s
• If you know the frequency you can calculate the wavelength and…
• What do different wavelengths relate to?
DIFFERENT COLORS
• Each different color has a different wavelength.
• How does electromagnetic radiation with a short wavelength effect you?
• How does electromagnetic radiation with a long wavelength effect you?
review the spectrum…
How are wavelength and frequency related???
…as the length of the wave increases the
frequency_______________.
The Photoelectric Effect
• When light shines on certain metals an electric current is produced (electrons are emitted from the metal).
• Only light of a certain minimum frequency can cause electrons to move.
• This could not be explained by the wave theory of light…
Quantum• A small specific amount of energy.• The minimum amount of energy that can
be lost/gained by an atom.• The energy of a quantum is related to its
frequency.E = h f
Energy = Plank’s constant x frequencyh = 6.626 x 10-34 j . s
• Higher frequency higher energy
• Shining light on a metal can liberate electrons from it’s surface.•Easy for violet (high frequency) difficultor impossible for red light (low frequency).
•E = h f …the energy of the light is related to it’s frequency ( high f = high E).•Einstein explained the photoelectric effect…light has a particle nature. High frequency light (violet) consists of ‘particles’ with a high energy (think bowling balls) low frequency light (red) consists of ‘particles’ with a low energy(think ping pong balls).•Particles of light are called photons… defined as a quantum of light energy.
Answer The Following
• Pg 97 # 1,4 & 5• Pg 118 # 4, 6• Pg 119 # 31, 32
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