CHM 108SuroviecFall 2015

Quantum Mechanical Model

I. Quantum Mechanics

Small is a relative term, but we use it to show size.

There is a limit to how we can use it in science.

2

II. Nature of Light

A. Wave Nature of lightLight is electromagnetic radiation. A type of energy embodies in oscillating electric and magnetic fields

3

A. Wave Nature of Light

An EM wave can be characterized by its amplitude and wavelength.

4

A. Nature of Light

All waves are also characterized by frequency ()

5

B. The EM Spectrum

The EM Spectrum is made of several different wavelengths

6

C. Interference and Diffraction

Waves (including EM waves) interact with each other in a characteristic way called interference

7

07_06.JPG8

D. Particle Nature of Light

In the early 1900s light was believed to be wave only, but then the photoelectric effect was discovered.

9

Example

A DVD player uses a laser that emits light at 685nm. What is the energy of 1 mole of photons of this light?

10

III. Atomic Spectroscopy and the Bohr Model

The dual nature of light led scientists to think about how light acts as both a particle and as a wave.

Atomic Spectroscopy was developed to explore the phenomenon.

11

07_10.JPG12

III. Atomic Spectroscopy and the Bohr Model

The idea that each element has discreet lines required scientists, like Neils Bohr, to develop a new model for the atom.

13

IV. Wave Nature

It has been shown that the wave nature of an electron is an inherent property of an individual electron.

A.deBroglie WavelengthAn electron traveling through space has a

wave nature.

14

Example

Calculate the wavelength in nm of an electron with speed 4.57 x 106 m/s

15

B. Uncertainty Principle

Experiments have shown that we can never see the interference pattern and simultaneously determine which hole the electron goes through to make it.

16

C. Indeterminacy 17

Macroscopic objects have their velocity and position known : determined.

Electrons do not (Uncertainty Principle): indeterminacy

V. Quantum Mechanics and the Atom18

Many properties of an element is dependent on the energy of electrons which is related to the velocity which we have shown to be indeterminate.

A.Schrodinger EquationThe wave function ψ is away to describe

energy of electrons and the probability of finding an electron in a volume of space.

1. Principle Quantum Number (n)19

The integer that determines overall size and energy of an orbital.

2. Angular Momentum Quantum Number (l)

20

This number determines the shape of the orbital.

2. Angular Momentum Quantum Number (l)

21

3. Magnetic Quantum Number (ml)22

This number tells us the orientation of the orbital

ml = -1 ml = 0 ml = 1

ml = -2 ml = -1 ml = 0 ml = 1 ml = 2

4. Magnetic Spin Number (ms)25

The spin of the electron in the orbital

Examples26

How many 2p orbitals are there in an atom?

How many electrons can be placed in the 3d sublevel?