1. Electrons in Atoms Chapter 5: Today we will learn:
5.3:Physics of the Quantum
Mechanical model
Electromagnetic spectrum
Light
Atomic Spectra
Quantum Mechanics
Chemistry _ Notes
Dr. Chirie Sumanasekera
10 /24/ 2017

2. 1. Electro magnetic spectrum

3. 1. Electro magnetic (E.M.) spectrum
Electro magetic spectrum:
The total spectrum of radiation from radio waves to gamma rays
The energy and frequency of the waves are proportional ( they increase or decrease together)
But the Amplitude is inversely proportional to the Frequency (or energy). This means that when the Amplitude increases the frequency and energy decreases, and vice versa.

4. 1. Electro magnetic (E.M.) spectrum
Light:
Is both a particle and a wave
Particles of light are called “photons”
It is a form of electromagnetic radiation
Sun light is made up of a spectrum of color, each with a different wave length (the rainbow colors). Red has the lowest energy, frequency and highest wave length. Violet has highest frequency, energy and the lowest wave length.
When sunlight passes through a prism, the mixture of colors separate based on wave length
The speed of light is x 108 m/s

5. Atomic spectra
When atoms absorb energy, electrons move from their usual principal energy level (ground state) to a higher principal energy level. Then, electrons lose this energy by emitting it as light energy as they approach ground state.
Atomic spectrum = the range of specific E.M. radiation frequencies emitted or absorbed by an atom
Each atom has a distinct Atomic spectrum that is unique to each element.
Atomic spectra can be used to identify the composition of unknown mixtures of metals, chemicals and even the make up of distant planets

6. Hydrogen Atomic spectrum
Lyman series
Ultra violet radiation emitted when electrons reach, n=1
Balmer series
Visible light emitted when electrons reach, n=2
Paschen series
Infrared radiation emitted when electrons reach, n=3
E = h. v
E = amount of quantum energy released
v = frequency
h= Plank’s constant (6.626 x JS)

7. 3. Quantum mechanics
Classical mechanics describes the motion of bodies larger than electrons while quantum mechanics describes the motion of atoms and sub atomic particles as waves.
Heisenberg’s uncertainty principle:
it is impossible to know exactly the velocity and the position of a particle at the same time.
This principle does not a[ply to large bodies.