1. Chemistry “Electrons in Atoms”

2. 1913 – Niels Bohr
proposed that the energy of the electron in the H atom was quantized
allowed energy levels for the electron = ORBITS
(electron can only have certain amounts of energy, not any possible amount)

3. Niels Bohr - Bohr Model
RULE 1: Electrons can orbit only at certain allowed distances from the nucleus.
RULE 2: Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. Also, an atom absorbs energy when an electron gets boosted from a low-energy orbit to a high-energy orbit.

4. Bohr’s Model of the atom

5. Excited state-describe an electron that has become excited
Electron Orbitals
Ground state-the original energy level of an electron before becoming excited
Excited state-describe an electron that has become excited

6. Photons
Photons are a particle of radiation or an individual quantum of light
Quantum is a finite quantity of energy that can be gained or lost by an atom

7. Practice Question
Using the Bohr’s Model of the atom, if an electron in an atom of hydrogen goes from energy level 6 to energy level 2,  what is the wavelength and frequency of the EM radiation emitted?

8. Practice Bohr’s Model
Which transition occurs when a hydrogen atom emits light with a wavelength of 434 nm?
A) The electron jumps from n=2 to n=4
B) The electron jumps from n=2 to n=5
C) The electron falls from n=4 to n=2
D) The electron falls from n=5 to n=2

9. 1926 – Erwin Schrödinger
applied known wave equations to electrons

10. Quantum Mechanical Model
In 1926 the Quantum Model was formed
It states that electrons do not have precise orbits or paths
Electrons move about in a cloud around the nucleus in what appears to be a random pattern
The Quantum Model only predicts where an electron is likely to be found

11. Heisenberg Uncertainty Principle
Heisenberg stated that you may know the location of an electron or the velocity of electron but you may not know both simultaneously

12. Quantum Model of the Atom
In the quantum model, the nucleus is not surrounded by orbits, but by atomic orbitals
Atomic Orbitals: a 3-D (three dimensional) region around the nucleus where a certain electron can be located
Begin 7th

14. Explanation of the Quantum Theory

15. Quantum Mechanical Model
Electrons emits energy in the form of radiation
Low energy electrons are found near the nucleus; 
high energy electrons are found further away from the nucleus

16. The Quantum Model is based on understanding the behavior of light
Light is composed of Electromagnetic (EM) waves
EM spectrum shows all forms of radiation

17. Electromagnetic Spectrum

18. Electromagnetic Spectrum
Encompasses all forms of electromagnetic radiation, with the only differences in the types of radiations is their frequencies and wavelengths.
The Speed of Light remains the same always.

19. Waves Wavelength: () the distance between wave crests
measured in m or nanometers (nm)
Amplitude: height of wave from origin to crest
Trough-the lowest point on a wave
Crest-the highest point on a wave

21. Frequency is measured in Hertz (Hz) 1 Hertz = 1/s
Frequency: () the number of wave cycles that pass a given point in a given time
Frequency is measured in Hertz (Hz)
1 Hertz = 1/s