Atomic Structure and Periodicity

1
Atomic Structure and Periodicity

• Electromagnetic Radiation and Nature of Matter

2
Quantum Theory

• From Democritus to Einstein has come the modern
  atomic theory.
• What is the nature of atoms? Remember Daltons
  theory?

3
Electromagnetic Radiation

• One way energy travel through space is via
  electromagnetic radiation.
• All forms of radiant energy have wavelike
  behavior.

4
Waves

• Waves have 3 characteristics
• Wavelength
• Frequency
• Speed

5
Wave characteristics

• ? is the symbol for wavelength, the distance
  between two consecutive peaks.
• ? is the frequency and is number of waves that
  pass through a given point in space in 1 second.
• The speed of all electromagnetic radiation is the
  speed of light or c.

6
Wavelength and Frequency

• The longer the wavelength, the shorter the
  frequency.
• ? ? ?
• ?? c
• Units for ? are 1/sec or hertz, Hz.

7
Waves have energy!

• Microwaves passing through water transfer their
  energy to the water and eventually heating the
  water to boiling.
• Fire transfers heat by infrared radiation.
• Which is higher energy? Red or blue light?

8
Flame tests!

• Example
• Sr(NO3)2 gives off a red flame of ? 650 nm.
• What is its frequency?

9
Answer

• ?? c or ? c/?
• ? 6.50 nm x 102
• C 2.9979 x 108 m/s
• 1 m 1 x 109 nm
• ? 4.61 x 1014 Hz

10
Nature of Matter

• 19th century thought Matter and energy are
  distinct.
• Matter was made of particles.
• Light was an energy that moved in waves.
• With that the study of physics was complete,
  there would be no new information, or was there?

11
Max Planck

• Studied radiation of soft bodies heated to
  incandescence. (light)
• Originally thought matter could absorb or emit
  any quantity of energy.
• Max found that the energy could only be gained or
  lost in whole number multipliers of the equation
  h?

12
Plancks Constant

• h is Plancks constant and was found to equal
  6.626 x 10-34 J?s.
• The change in energy for a system may be found by
  ?Enh?
• This equation states that energy is given off in
  packets or quantized.
• Each packet of energy is a quantum.

13
Example

• The blue in fireworks is often from Copper (I)
  chloride heated to 1200C. Blue light has a
  wavelength of 450 nm. What is the quantum of
  energy that may be emitted by light at 450 nm?

14
Answer

• ?Enh? n1
• ? c/?
• 2.9979 x 108 m/s
• 4.5 x 10-7 m
• 6.6x10 14 s-1