Download Chapter 4: Electrons in Atoms I. Properties of Light A

Chapter 4: Electrons in Atoms
I. Properties of Light
A. Electromagnetic Radiation- form of energy that exhibits wavelike behavior
1. Many types of EM waves- make up the electromagnetic spectrum
a. visible light
d. infrared light
b. x-rays
e. radio waves
c. ultraviolet light
2. EM radiation are forms of energy which move through space as waves
a. Move at speed of light (c)
(1). c= 3.00 x 10^8 m/s
b. Speed is equal to the frequency times the wavelength c = νλ
(1). Freqency (ν) is the number of waves passing a given point in one second, measured in Hz or
s^-1
(2). Wavelength (λ) is the distance between two corresponding points on adjacent waves
c. Speed of light is a constant, so νλ is also a constant
(1) ν and λ must be inversely proportional; when one goes up, the other goes down.
B. Photoelectric Effect- emission of electrons from a metal when light shines on the metal (light is particle-like)
1. Radiant energy is transferred in units (or
2. Energy of a photon is directly
quanta) of energy called photons
proportional to the frequency of radiation
a. A photon is a particle of energy
a. E = hν (h is Planck’s constant,
having a rest mass of zero and
6.62554 x 10 -27 erg sec)
carrying a quantum of
energy
b. A quantum is the minimum
amount of energy that can be lost
or gained by an atom
II. Atomic Spectra
A. Ground State
1. The ________________ energy state of an atom
B. Excited State
1. A state in which an atom has a _________________ potential energy than in its ground state
C. Bright line spectrum
1. Light is given off by excited atoms as they
3. A spectroscope reveals lines of particular
return to lower energy states
colors
2. Light is given off in very definite
wavelengths
III. The Bohr Model of the Atom
A. Electron Orbits, or Energy Levels
1. Electrons can circle the nucleus only in allowed paths or ________________
2. The energy of the electron is greater when it is in orbits _________________ from the nucleus
3. The atom achieves the ground state when atoms occupy the closest possible positions around
the nucleus
4. Electromagnetic radiation (photon) is emitted when electrons move ___________ to the nucleus
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B. Energy transitions
1. Energies of atoms are fixed and definite
quantities
2. Energy transitions occur in jumps of
discrete amounts of energy
3. Electrons only lose energy when they
move to a ________________ energy state,
this is called Emission
4. Electrons gain energy when they move to
higher energy levels, this is called
__________________
C. Shortcomings of the Bohr Model
1. Doesn't work for atoms larger than hydrogen (more than one electron)
2. Doesn't explain chemical behavior
IV. The Quantum Mechanical Model
A. Electrons as Waves
1. French scientist _________________________ suggested that electrons be considered waves
confined to the space around an atomic nucleus.
2. According to the relationship E = hν, these frequencies corresponded to specific
________________—the quantized energies of Bohr’s orbits.
B. Heisenberg Uncertainty Principle
1. German physicist Werner Heisenberg proposed that any attempt to locate a specific
_______________ with a photon knocks the electron off its course.
Translated: “The more certain I am about where it is, the less certain I can be about
where it is going. The more certain I am about where it is going, the less certain I can be
about where it is.”
2. The Heisenberg uncertainty principle states that it is impossible to determine simultaneously both
the _________________________ of an electron or any other particle.
C. Schrodinger Wave Equation
1. In 1926, Austrian physicist ___________________ developed an equation that treated electrons in
atoms as waves.
2. Quantum theory describes mathematically the wave properties of electrons and other very small
particles.
D. Electrons do not travel around the nucleus in neat orbits, as Bohr had postulated.
1. Instead, they exist in certain regions called ________________.
V. Atomic Orbitals
A. Atomic orbital
1. An orbital is a three-dimensional region around the nucleus that indicates the probable
location of an electron.
B. Quantum numbers specify the properties of atomic orbitals and the properties of electrons in orbitals.
1.
2.
3.
4.
The principal quantum number, symbolized by n, indicates the main ___________________
occupied by the electron.
The angular momentum quantum number, symbolized by l, indicates the ________________ of
the orbital.
a. Shapes in the first four shells are designated s, p, d, f
The magnetic quantum number, symbolized by m, indicates the orientation of an orbital around
the nucleus.
The spin quantum number has only two possible values—(+1/2 , −1/2)—which indicate the two
fundamental _________________________ of an electron in an orbital.
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