the arrangement of electrons in atoms the development of the new atomic model

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