1. Electrons in Atoms
Chapter 4

2. RUTHERFORD MODEL

3. A NEW ATOMIC MODEL
The ____________ model of the atom was a great improvement, but it was incomplete.
In the early 20th century, a new model was evolving based on the ________________ and ________________ of light by matter.
The studies revealed a very intimate relationship between ______________ and ______________.
Rutherford
emission
absorption
electrons
light

4. Chemists found Rutherford’s nuclear model an improvement but more experiments were being conducted.
In the early 1900s, scientists began to unravel the puzzle of chemical behavior.
The had observed that certain elements emitted ____________________ when heated in a flame.
Visible Light

5. PROPERTIES OF LIGHT Electromagnetic Radiation 3.00 x 108
Before 1900, light was thought be behave solely as a __________.
___________________________ is a form of energy that exhibits wave-like behavior as it travels through space – ALL FORMS travel at the speed of light: ____________ m/s
Including Gamma Rays, X-Rays, Ultraviolet, Visible Light, Infrared, Microwaves, and Radio Waves (AM and FM) (listed in order of strength)
wave
Electromagnetic Radiation
3.00 x 108

6. ELECTROMAGNETIC SPECTRUM

7. VISIBLE LIGHT
The visible spectrum includes the colors: ______, ______, __________, ________, _________, ____________, and ____________. (ROY G BIV)
Red
Orange
Yellow
Green
Blue
Indigo
Violet

8. The significant feature about waves is their ______________ nature.
repetitive

9. CHARACTERISTICS OF WAVES
Wavelength
____________________ is the distance between corresponding points on adjacent waves. It is measure in ______________________.
Nanometers (nm)

10. Frequency
________________ is the number of waves that pass a given point in a specific time, usually “per second.” It is measured in _____________ (Hz).
Hertz

11. INVERSE RELATIONSHIP

12. PARTICLE THEORY OF LIGHT
In the 1900s, scientists conducted _____ experiments that could not be explained by the wave theory of light. 2

13. 1. Photoelectric Effect electrons
The Photoelectric Effect refers to the emission of ______________ from a metal when light shines on that metal. The mystery is that this would only happen if the light’s frequency was above a certain ____________, regardless of how long the light shone on it.
According to the ___________ Theory, light should have been able to know electrons loose no matter what frequency.
electrons
minimum
Wave

14. In 1900, the German Physicist, _______________ (1858 – 1947) began searching for an explanation as he studied the light emitted from heated objects.
Max Planck

15. Max Planck suggested that Electromagnetic Energy was NOT ___________ like a wave, but was in small, specific bursts.
A _________ is the minimum amount of energy that can be lost or gained by an electron.
He demonstrated mathematically that the energy of a QUANTUM is related to the frequency of the emitted radiation by the equation where E is energy and h is Planck’s constant, and v is frequency.
continuous
Quantum

17. DUAL WAVE-PARTICLE THEORY OF LIGHT
Albert Einstein furthered the new theory suggesting that light had a ____ _____________ quality.
He used the term __________ as a particle of electromagnetic radiation having zero mass and carrying a quantum of energy.
Dual
Wave-Particle
photon

19. DUAL WAVE-PARTICLE THEORY OF LIGHT

20. 2. BOHR AND THE HYDROGEN LINE EMISSION SPECTRUM
Terminology:
Ground State: the lowest energy state of an atom.
Excited State: the state at which an atom has a higher energy level than it’s ground state
Emission: when an excited atom returns to ground state, it gives off energy in the form of electromagnetic radiation.
Ex. Neon signs, fireworks!

21. Neils Bohr (1913) experimented with ______________.
“Excited” hydrogen gives off a _______ glow.
He narrowed the beam and put it through a prism and expected a _____________________, like a rainbow.
This did not happen.
hydrogen
pinkish
continuous spectrum

23. Was not a continuous spectrum
Gave off only specific frequencies of light
Lead to the :

24. Energy
Movement of Electrons
Example
Light?
Required?
Absorption
Absorbed
Lower to higher energy level
N = 1 to n = 3 No
Yes
Emission
Released
Higher to lower energy level
N = 4 to n = 2

27. What color is the light when a hydrogen atom falls from n = 4 to n = 2
What color is the light when a hydrogen atom falls from n = 4 to n = 2? (look on reference table, last page
Blue!

28. BOHR MODEL Still using today: ___________________ Energy levels
Shortcomings:
1. Only used hydrogen
2. Said electrons “orbited” the nucleus
Energy levels