Development of Atomic Models
Where are the electrons exactly?
propeller has equal
probability of being
anywhere in the
blurry region, but…
…you cannot tell
its exact location at
any instant.
Quantum Mechanical Model (Electron Cloud)
(1926–Erwin Schrodinger & others)
• shows most
probable
locations of
electrons
•equations
describe
electrons as
waves in motion
through space
Quantum Mechanical Model
The electron is visualized not as a particle at
some location in the atom, but its mass and
charge are spread as a standing wave
around the nucleus.
energy levels 1,2,3,4
straightened out
Quantum Mechanical Model
a. Bohr’s model shows electrons orbit the nucleus
like planets going around the sun.
b. de Broglie’s idea shows a wave along an orbit.
c. Quantum Mechanical model:
electrons are in a 3D “cloud” of orbits of
wave equations (math) and probability.
5.2 levels have
Atomic Orbitals
energy
sublevels of different
shapes (not perfect rings)
Atomic Orbitals
energy levels have sublevels of
different shapes (not perfect rings
like Bohr proposed)
5.2 levels have
Atomic Orbitals
energy
sublevels of different
shapes (not perfect rings)
Atomic Orbitals
energy levels have sublevels of
different shapes (not perfect rings
like Bohr proposed)
atomic orbitals: 3-D regions with a high
probability of electrons
s orbitals
are
spherical
d
f
p orbitals are dumbbell-shaped
in 3 directions
Electron energy levels have
sublevels of different shapes
Nucleus
2s
orbital
2p
orbitals
1s
orbital
3s
orbital
Development of Atomic Models
1803 Dalton
1904 Thomson
1911 Rutherford
1913 Bohr
1926 Quantum Mechanical
Model
Quick Quiz!
1. What does the quantum mechanical model
describe about atoms?
A. the probable locations of electrons in
atoms
B. the precise locations of electrons in
atoms
C. the number of electrons in an atom
D. how crazy chemistry is
Quick Quiz.
2. What do orbitals (s, p, d, f) tell us about
the sublevel of an electron?
A. the amount of energy in each electron
B. the number of electrons in each
sublevel
C. the shape of the region they occupy
D. that my brain feels mushy now