Section 5.1
5.1
The Development of Atomic
Models

The timeline shoes the development of atomic models from
1803 to 1911.
5.1
The Development of Atomic
Models

The timeline shows the development of atomic models from
1913 to 1932.
What was wrong with Rutherford’s
Model?
 Think back to Rutherford’s Gold foil experiment.
 What did Rutherford say about the atom?
 Atoms mostly empty space
 Nucleus dense and positive
 Electrons orbit the nucleus like planets orbit the sun
 Rutherford’s model did not explain chemical
properties of elements
 His model also did not explain why objects change color
when heated
Bohr’s Model & Schrodinger’s
Model- Current model
 Bohr’s Model:
http://player.discoveryeducation.com/index.cfm?guid
AssetId=5250e1fc-78dc-498b-824c-fdea514a575c
 Schrodinger’s Model:
http://player.discoveryeducation.com/index.cfm?guid
AssetId=5250e1fc-78dc-498b-824c-fdea514a575c
Bohr’s Model
 Bohr proposed that an electron is found only in specific
circular paths, or orbits, around the nucleus.
 Each possible electron orbit in Bohr’s model has a
fixed energy.
 The fixed energies an electron can have are called
energy levels.
 A quantum of energy is the amount of energy required
to move an electron from one energy level to another
energy level.
5.1
The Bohr Model
 Like the rungs of the strange
ladder, the energy levels in an
atom are not equally spaced.
 The higher the energy level
occupied by an electron, the
less energy it takes to move
from that energy level to the
next higher energy level.
Current atomic model- Quantum
Mechanical Model
 Still has the nucleus containing protons and neutrons in
the center.
 Still has electrons outside the nucleus in a low density area
 The quantum mechanical model determines the allowed
energies an electron can have and how likely it is to find
the electron in various locations around the nucleus.
 This model is based on equations developed by Erwin
Schrodinger
5.1
The Quantum Mechanical Model

The propeller blade has the same probability of being
anywhere in the blurry region, but you cannot tell its
location at any instant. The electron cloud of an atom can
be compared to a spinning airplane propeller.
5.1
The Quantum Mechanical Model

In the quantum mechanical model, the probability of finding
an electron within a certain volume of space surrounding the
nucleus can be represented as a fuzzy cloud. The cloud is
more dense where the probability of finding the electron is
high.
Principle Energy Levels of Electrons
 Energy levels and # of electrons in each:
 Level 1 Holds 2
 Level 2 Holds 8
 Level 3 Holds 18
 Level 4 Holds 32
Principle energy levels are broken
down into sublevels called: Atomic
Orbitals
 An atomic orbital is often thought of as a region of
space in which there is a high probability of finding an
electron.
 Each energy sublevel corresponds to an orbital of a
different shape, which describes where the electron is
likely to be found.
 Each orbital contains up to 2 electrons
 Orbitals include: s, p, d, and f
5.1
Atomic Orbitals



Different atomic orbitals are denoted by letters. The s orbitals
are spherical, and p orbitals are dumbbell-shaped.
The s sublevel contains 1 orbital, so up to 2 electrons
The p sublevel contains 3 orbitals, so up to 6 electrons
5.1
Atomic Orbitals


Four of the five d orbitals have the same shape but different
orientations in space.
Since there are 5 orbitals, up to 10 electrons can be found in
the d sublevel.
Atomic Orbitals
 F orbitals. There are 7 with complex shapes. A few are
shown below:
 Since there are 7 orbitals, up to 14 electrons can be
found in the f orbitals.

file:///C:/Chemistry%20PresentationExpress/Chapter05/Section01/ChemASAP/dswmedia/rsc/asap1_chem05_cman0505.html
Orbital Summary
Sublevel
s
# of
#
Shape
Orbitals electrons
in
sublevel
1
2
Sphere
p
3
6
Dumbbell
d
5
10
Double Dumbbell
f
7
14
Complex shapes
Summary of Energy Levels and Orbitals
Principle
Energy Level
# of
Sublevels
Identity of
Sublevels
# of orbitals
Max. # of
electrons
1
1
s
1
2
2
2
s, p
1+ 3=4
8
3
3
s, p, d
1+3+5 = 9
18
4
4
s, p, d
1+3+5+7 = 16
32
Periodic Table Showing Locations
of some electrons
The n represents the principle energy level
The values for “n” are the same as the period numbers.
Notice the s block has 2 columns because s can hold 2 electrons.
The d block has 10 columns because d can hold up to 10 electrons
The p block has 6 columns because p can hold up to 6 electrons