The AtomThe Atom

Chapter Chapter 99

Homework AssignmentHomework AssignmentChap 9Chap 9

Review Questions (p 187): 1 – 22Review Questions (p 187): 1 – 22

Multiple Choice Questions: 1 - 3Multiple Choice Questions: 1 - 3

Visible light consists of electromagnetic waves

Electromagnetic radiation: emission and transmission of energy in the form of electromagnetic waves.

Speed of light (c) in vacuum = 3.00 x 108 m/s

Fig. 8.11

Fig. 8.10 The Electromagnetic Spectrum

White light is separated into its color

components by a prism

Fig 9.10 (a)

White light is separated into its color

components by a diffraction grating

Fig 9.10 (b)

The tracks of a compact disc act as a diffraction grating,producing a separation of the colors of white light.

 

                          

                                    

Line Emission Spectrum of Hydrogen Atoms

Atomic Emission Spectra

7.3

First recorded emission spectrum of the sun

intensity

wavelength

1. e- can only have specific (quantized) energy values

2. light is emitted as e- moves from one energy level to a lower energy level

Bohr’s Conceptual Model of the Atom

(1913)

n (principal quantum number) = 1,2,3,…

Fig 9.19

e-

E = h

E = h

Low energyHigh energy

Egreen > Ered

Fig 9.18

Why is e- energy quantized?

Standing or stationary wavesStanding or stationary waves

Fig. 7.10Fig. 7.10

nodes nodes

De Broglie (1924) reasoned that e- is both particle and wave.

Why is e- energy quantized?

Fig 9.21

This is a matter wave,

not an em wave!

Standing or stationary wavesStanding or stationary waves

nodes nodes

Zero probability of finding the electron

Maximum probability of finding the electron

Dual nature of the electronDual nature of the electron

• How can we locate a particle if it behaves as a wave?!How can we locate a particle if it behaves as a wave?!

• The uncertainty principleThe uncertainty principle::

• It is impossible to know simultaneously the energyIt is impossible to know simultaneously the energy

and the position of a particle.and the position of a particle.

• We choose to know the We choose to know the energyenergy as precisely as possible as precisely as possible

• Refer to “position” of electron in terms of Refer to “position” of electron in terms of probabilityprobability..

Where 90% of thee- density is foundfor the orbital

Fig 9.22 (a) Fig 9.22 (b)

s orbitals

p orbitals

d orbitals

Fig 9.2

Part of Fig 9.27 According to the Shell Model

Valence electrons ≡ electrons in outermost shell