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Transcript
BOHR MODEL AND
QUANTUM NUMBERS
October 28,
2014
BOHR’S MODEL
Why don’t the electrons fall into the
nucleus?
Move like planets around the sun.
In circular orbits at different levels.
Amounts of energy separate one level
from another.
When electrons are hit with energy (flame,
heat) they jump to a different level.
BOHR’S MODEL
Nucleus
Electron
Orbit
Energy Levels
BOHR POSTULATED THAT:




Fixed energy related to the orbit
Electrons cannot exist between orbits
The higher the energy level, the further it is away from the
nucleus
An atom with maximum number of electrons in the
outermost orbital energy level is stable (unreactive)
Increasing energy
Fifth
Fourth
Third
Second
First
 Further away
from the
nucleus
means more
energy.
 There is no
“in between”
energy
 Energy
Levels n=
1,2,3,4,5,6,7
HOW DID HE DEVELOP HIS THEORY?
 He used mathematics to explain the
visible spectrum of hydrogen gas
 http://www.mhhe.com/physsci/chemis
try/essentialchemistry/flash/linesp16.
swf
THE LINE SPECTRUM
electricity passed
through a gaseous
element emits
light at a certain
wavelength
Can be seen when
passed through a
prism
Every gas has a
unique pattern
(color)
LINE SPECTRUM OF VARIOUS
ELEMENTS
THE QUANTUM MECHANICAL MODEL
Energy is quantized. It comes in chunks.
A quantum is the amount of energy needed to
move from one energy level to another.
Since the energy of an atom is never “in
between” there must be a quantum leap in
energy.
Schrödinger derived an equation that
described the energy and position of the
electrons in an atom
ATOMIC ORBITALS
Principal Quantum Number (n) = the energy
level of the electron.
Within each energy level the complex math
of Schrödinger's equation describes several
shapes.
These are called atomic orbitals
Regions where there is a high probability of
finding an electron
SUBLEVELS OF ENERGY
 s orbitals (sphere)
 p orbitals (dumbbell)
 d orbitals (5 dif ferent shapes)
 f orbitals (hard to visualize)
SUBLEVELS, ORBITAL AND NUMBER OF
ELECTRONS
 SUBLEVEL
NUMBER OF ORBITALS
S
1
p
3
d
5
f
7
To determine the number of electrons in a sublevel, we use the
formula 2n 2 where “n” energy level that is outside of the
nucleus.
S ORBITALS
1 s orbital for
every energy level
1s
2s
3s
Spherical shaped
Each s orbital can hold 2 electrons
Called the 1s, 2s, 3s, etc.. orbitals
P ORBITALS
 Start at the second energy level
 3 different directions
 3 different shapes
 Each orbital can hold 2 electrons
The p Sublevel
has 3 p orbitals
THE D SUBLEVEL CONTAINS 5 D
ORBITALS rd
 The D sublevel starts in the 3 energy level
 5 different shapes (orbitals)
 Each orbital can hold 2 electrons
THE F SUBLEVEL HAS 7 F ORBITALS
 The F sublevel starts in the fourth energy level
 The F sublevel has seven different shapes
(orbitals)
 2 electrons per orbital
SUMMARY
Starts at
energy
level
Sublevel
# of shapes
(orbitals)
Max # of
electrons
s
1
2
1
p
3
6
2
d
5
10
3
f
7
14
4
ELECTRON CONFIGURATIONS
 The way electrons are arranged in atoms.
 Aufbau principle- electrons enter the lowest energy first.
 This causes dif ficulties because of the overlap of orbitals of
dif ferent energies.
 Pauli Exclusion Principle - at most 2 electrons per orbital dif ferent spins
ELECTRON CONFIGURATIONS
First Energy Level
 only s sublevel (1 s orbital)
 only 2 electrons
 1s 2
Second Energy Level
 s and p sublevels (s and p orbitals are available)
 2 in s, 6 in p
 2s 2 2p 6
 8 total electrons
Third energy level
s, p, and d orbitals
2 in s, 6 in p, and 10 in d
3s 2 3p 6 3d 10
18 total electrons
Fourth energy level
s,p,d, and f orbitals
2 in s, 6 in p, 10 in d, and 14 in f
4s 24p 6 4d 10 4f 14
32 total electrons
GREAT SITE TO
PRACTICE AND
INSTANTLY SEE RESULTS
FOR ELECTRON
CONFIGURATION.