Arrangement of Electrons in Atoms

- Development of a New Atomic Model

Wave Description Of Light

- Electromagnetic Radiation
- form of energy that exhibits wavelike behavior as

it travels through space. - EX visible light, X-ray, Ultraviolet and

inferred light, microwaves, and radio waves. - Travels at a constant speed of 3.0 x 108 m/s
- Electromagnetic Spectrum All the electromagnetic

radiation form the ES. (fig 4-1, p. 92)

Electromagnetic Spectrum

Wave Calculations

- Wavelength (?) - distance between two peaks .

Measured in meters - Frequency (v) - number of peaks that pass a point

each second. - Hz Hertz s-1
- c ? v
- where c 3.0 x 108 m/s

Is light really a wave?

- Max Planck did experiments with light-matter

interactions where light did not act like a wave - Photoelectric Effect - emission of electrons from

a metal when light shines on the metal. - Only emitted at certain energies wave theory

said any energy should do it. - Led to the particle theory of light

- Planck suggested that objects emit energy in

specific amounts called QUANTA - Quantum - minimum quantity of energy that can be

lost or gained by an atom. - led Planck to relate the energy of an electron

with the frequency of EMR - E hv
- E Energy (J, of a quantum of radiation)
- v frequency of radiation emitted
- h Plancks constant (6.626 x 10-34 Js)

Equation Practice

- What is the frequency of yellow light with a

wavelength of 548 nm?

Equation Practice

- What is the wavelength of blue light with a

frequency of 4.60 x 1023 Hz?

Equation Practice

- What is the energy of magenta light with a

wavelength of 691 nm?

- leads to Einsteins dual nature of light (EMR

behaves as both a wave and a particle) - Photon - particle of EMR having zero mass and

carrying a quantum of energy.

Hydrogen Emission Spectrum

- Ground State - Lowest energy state of electron.
- Excited State - higher energy than ground state.
- Bright-line Spectrum (emission spectrum)
- Series of specific light frequencies emitted by

elements - "spectra are the fingerprints of the elements"

The Development of A New Atomic Model

- Rutherfords model was an improvement over

previous models, but still incomplete. - Where exactly are electrons located?
- What prevented the electrons from being drawn

into the nucleus?

Bohr Model Of H Atom

- Bohr explained how the electrons stay in the

cloud instead of slamming into the nucleus - Definite orbits paths
- The greater the distance from the nucleus, the

greater the energy of an electron in that shell.

- Electrons start in lowest possible level - ground

state. - Absorb energy - become excited and shift upward.
- Dropping back down - emits photons (packets of

energies equal to the previously absorbed

energy). - Hydrogen Emission Spectrum

Quantum Model of the Atom

- Bohrs model was great, but it didnt answer the

question why? - Why did electrons have to stay in specific

orbits? - Why couldnt the electrons exist anywhere within

the electron cloud? - Louis de Broglie pointed out that electrons act

like waves - Using Plancks equation (Ehv), dB proved that

electrons can have specific energies and that

Bohrs quantized orbits were actually correct

Heisenberg Uncertainty Principle

- Impossible to determine both the exact location

and velocity of an electron

Schrodinger Wave Equation

- He gave more support to Bohrs quantized energy

levels - Quantum theory describes the wave properties of

electrons using mathematical equations - Disproved Bohrs train tracks within those

energy levels