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Chapter 5: Arrangement of Electrons
I. Modern Atomic Theory
A. Neils Bohr (1885 – 1962) – Danish Physicist
1. Improved Rutherford’s work by saying electrons do not lose energy in the atoms so they will stay
in orbit.
2. Stated there are definite levels in which the electrons follow set paths without gaining or losing
energy (Planetary Model).
3. Each level has a certain amount of energy associated with it and the electrons can only jump
levels if they gain or lose energy
4. Lowest energy levels closest to nucleus
a. In the ____________________________ for an atom, electrons are at their lowest, most
stable energy levels.
b. In the ____________________________, atoms require energy and electrons move to a
higher energy level.
B. Max Planck (early 1858 – 1947) – German Physicist
a. Proposed __________________________________ which says that energy is given off in little
packets or particles called ___________________ which are based on the particle nature of light.
b. Each quantum of energy corresponds to the different energy levels for electrons.
c. Proposed the equation: E=hf, where E is energy, f is frequency, and h is Planck’s constant
(6.626 x 10-34 J•s).
C. Louis de Broglie (1892 – 1987) – French Physicist
1. Suggested that if waves can have a particle nature, particles can have a wave nature, known as
the “___________________________________” principle.
2. Wondered why the positive nucleus and negative electrons do not attract. Proposed that electrons
moved so fast (speed of light) that they had properties of ______________ instead of particles.
3. The Study of Waves
a. Definition of a wave: a progressive disturbance propagated from point to point in a
__________________ or __________________ without progress or advance by the points
themselves
b. Types of Waves
1.) ___________________: a wave that requires an energy source and an elastic
material medium to travel.
2.) ___________________ (EM): a wave that does not require a material medium to
travel; it propagates by electric and magnetic fields.
c. Wave Travel
1.) Transverse: displacement of the medium is ____________________ to the direction
of propagation of the wave.
2.) Longitudinal: displacement of the medium is _____________________ to the
direction of propagation of the wave
d. Properties of Waves
1.) ___________________ (λ): The distance between any part of the wave (peak) and the
nearest part that is in phase with it (another peak). Standard unit is meters (m).
2.) ____________________ (f ): The number of peaks which pass a given point each
second. Standard unit is cycles per second which is a hertz (Hz).
3. _____________________ (A): The maximum displacement of a vibrating particle from
its equilibrium position. Standard unit is meters (m).
4. ____________________ (c): the distance a wave (peak) travels in a given time.
Standard unit is meters per second (m/s).
5. ______________ (E): The energy of a single photon of radiation of a given frequency.
Standard unit is the joule (J).
c = λf
→ For electromagnetic waves, the velocity (c) is 3.00 x 108 m/s
E= hf
→ h is Planck’s Constant = 6.626 x 10-34 J•s
C. Werner Heisenberg (1901 – 1976) – German Physicist
a. Proposed his “___________________________________”, which says that the position and
momentum of an electron cannot simultaneously be measured and known exactly.
b. The arrangement of electrons is discussed in terms of the _____________ of finding an electron
in a certain location.
D. Erwin Schrödinger (1887 – 1961) – Austrian Physicist
1. Studied the wave nature of the electron and developed mathematical equations to describe their
wave-like behavior.
2. The most probable location of the electrons can be found and the plot of this probability is called
the __________________________________.
3. The four quantum numbers
a.Principal Quantum Number (n)
1.) Refers to the _____________________ in the atom which is the distance from the
nucleus and designated with a positive whole number (n=1,2,3,4,5,6,7).
2.) Wavelength of emitted photon is determined by the “energy jump” between energy
levels.
3.) Energy levels (or shells) means electrons are contained in an area where the
probability of finding the electron is 90%.
b. Angular Momentum Quantum Number (l)
1.) Refers to the ________________ (within an energy level) which is one or more
“partitions” each with a slightly different energy.
2.) The types of sublevels: s, p, d, f, etc.
a. l = 0 (s sublevel)
b. l = 1 (p sublevel)
c. l = 2 (d sublevel)
d. l = 3 (f sublevel)
c. Magnetic Quantum Number (m)
1.) Refers to the orientation in space of the __________________ in a sublevel.
2.) Can have any whole number value from – l to + l which will tell how many orbitals
are in a sublevel.
3.) A maximum of 2 electrons per orbital.
Sublevel
s
p
d
f
# of Orbitals
Total # of electrons
d. Spin Quantum Number (s)
1.) Refers to the ______________ of the electron.
2.) Pauli Exclusion Principle: if two electrons occupy the same orbital, they must have
__________________________ spin.
Half-filled orbital:
_____
Filled orbital:
_____
Permissible Values of Quantum Numbers for Atomic Orbitals
n
l
m
Orbital
1
0
0
1s
1
1
2
2
0
1
0
-1,0,1
2s
2p
2
1
3
2
6
3
0
1
2
0
-1,0,1
-2,-1,0,1,2
3s
3p
3d
3
1
3
5
2
6
10
4
0
1
2
3
4s
4p
4d
4f
4
1
3
5
7
2
6
10
14
0
-1,0,1
-2,-1,0,1,2
-3,-2,-1,0,1,2,3
# of Subshells
#of Orbitals
Max # of Electrons
5. Distribution of Electrons for Different Elements (Electron Configuration)
a. Electrons will occupy the lowest energy levels and sublevels first.
b. Notation:
Principal Quantum
Number, n (energy
level)
Type of Orbital (sublevel)
c.
2
# of electrons
2p y
Orientation of
Orbital
_______________________: an electron occupies the lowest-energy orbital that can receive it.
d. Long Notation: “Rule of thumb” for filling electrons at the lowest energy level possible.
e. ________________________: orbitals of equal energy are each occupied by one electron before any
orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the
same spin state.
Give the long notation electron configuration for:
O
O2–
Ca
Ca2+
Ag
Give the short (or noble gas) notation
O
O2–
Ca
Ca2+
Ag
f. Orbital Diagrams: Usually only done for the outer shell electrons, which always include the
________________ and ______________ orbitals.
Give the orbital diagrams (arrow notation)
O
O2–
Ca
Ca2+
Ag
g. Electron Dot Diagrams: shows the _______________________ or valence electrons for elements.
Give the electron dot diagrams
O
O2–
Ca
Ca2+
Ag