1. Bohr’s Model of the Atom
Chapter 5

2. The Modern View of the Atom The atom is mostly empty space.
Two regions
The Nucleus – Protons and neutrons are located in the nucleus.
Electron cloud region – Place where you might find an electron.

3. The Atom is mostly empty space
From his measurements, Rutherford estimated the radius of an atom to be 100,000 times greater than the radius of the nucleus. This is comparable to the thickness of a dime to the length of football field

4. Max Planck’s Quantum Theory
What did Planck proposed?
Quanta = plural
Quantum = singular
Atom energy is absorbed or liberated in packets or chunks of energy. Planck called these packages of energy "quanta".

5. Photon
The Quantum of Light = the Photon.
Particles of light are called light quanta or photons.
Energy of a Photon = h x u E = h x u or E = h x f
h is Planck’s constant h = 6.63 x J.s
u is equal to the frequency of light u = f = frequency

6. Packet of energy in a photon is so small that we are not aware of the rain of photons of light impinging on our eyes –
just as you cannot feel the impact of individual air molecules.

7. The quantum concept Max Planck (1900) Einstein (1905)
Introduced quantized energy
Einstein (1905)
Light made up of quantized photons
Higher frequency photons = more energetic photons

8. Bohr’s atomic model Niels Bohr puts it all together
Bohr added Planck’s quanta idea (which was proven by Einstein and Louis de Broglie’s wave/particle theory) to the Rutherford’s atomic model.

9. Electrons exist at set levels of energy, at fixed distances from the nucleus.
When an atom absorbs energy, the electron jumps to a level further from the nucleus
If it radiated energy, that means that the electron is falling to a level closer to the nucleus.

10. The protons and neutrons are located in the nucleus.
The electrons are located at different energy shells (energy levels around the nucleus)

11. Energy Levels/shells
There are several energy levels in which an electron might be found.
To move from one level to another an electron must gain or lose an exact amount of energy. Quantum
2nd shell
1st shell e-
2 electrons e- e-

12. Bohr’s T heory Three rules:
Electrons only exist in certain allowed orbits
Within an orbit, the electron does not radiate
Radiation is emitted or absorbed when changing orbits