Niels Bohr (1913)

• Bright-Line Spectrum– tried to explain presence

of specific colors in hydrogen’s spectrum

• Energy Levels– electrons can only exist in

specific energy states

• Planetary Model

Orbits or Energy levels

• Area where e-

are trapped within an atom

• Atoms have multiple orbits

Electrons Produce Light!!

• Electrons (e-) move within atoms– (e-) movement is caused by

energy– (e-) move in different orbits

Photons

• A particle form of light or electromagnetic radiation

A photon walks into a hotel and checks in. "Do you want a hand with your luggage?" asks the receptionist. "No thanks", replies the photon, " I’m travelling light".

Excited state

1. Electrons jump to a higher orbit

2. Caused by atoms absorbing energy

Ground state

• Electron falls back to lower level (ground state)

• Energy is released as electromagnetic radiation (E.R) (photon)

Transition of n 3→2 4→2 5→2 6→2 7-2

Wavelength (nm) 650 500 450 425 400

color red blue green violet UV

Quantum or jump

•   when an e_ jumps orbits it transports to the next orbit!!!

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A photon can be released as any electromagnetic energy

Spectral lines summed up

1. e- are in fixed orbits

2. e- can get excited, and jump to a higher orbit, if they absorb the appropriate energy

3. e- will fall back to lower level (ground state) and release a photon of similar energy (visible light)

5 points of the Bohrs Model

– 1. elements produce spectral lines also known as energy levels

2. Energy levels are represented by letters

– 3. Energy levels get larger the farther away they are from the nucleus

–4. larger the energy level more electrons they can hold

–5 Each energy level can only hold so many electrons

Problems?

• Why do electrons they stay in their orbits?