Note that the periodic table is arranged based on the way electrons arrange themselves around the
nucleus of an atom (to differ from the idea that elements are solely based on atomic number). For
example, elements in Group 1 exhibit many similar physical properties including reactivity in
water.
The Bohr-Rutherford Diagram is useful for the first 20 elements. The quantum model does give us
a better understanding of atoms and their chemical properties.
For any atom, there are three ways in which energy contributes:
(1)
(2)
(3)
Multi-electronic atomic orbitals have the same general shape as orbitals of the hydrogen atom, but
there are obvious size and energy differences. Much has to do with the varying levels of attraction
and repulsion between subatomic particles in the atom.
For multi-electronic atoms, the energies of orbitals within the same energy level, n, are different.
For example:
<
<
<
ELECTRONIC STRUCTURE OF THE ATOM

The electronic structure of atoms can be represented by both electron configurations and
energy level diagrams which show the relative energies of the electrons in an atom.
The Aufbau Principle states:
ELECTRONIC CONFIGURATIONS
We can represent the
and
of
atoms and ions in an easier way. Note that electron configurations represent electrons in the
(lowest energy).
OR
ENERGY LEVEL (ORBITAL) DIAGRAMS
The diagram to the right is a convention to show
the relative energies of electrons in an atom. It
takes into consideration the quantum numbers
for each individual electron.
Draw an energy level diagram for a nickel atom?
Hund’s Rule - In order for electrons to have the lowest energy configuration, they
must occupy the energy orbital with
spins before adding
electrons with
spins. Basically,
GUIDELINES FOR WRITING ELECTRON CONFIGURATIONS:
Example 1:
Write the electron configuration for the element manganese, Mn?
Example 2:
Write the electron configuration for the aluminum ion? Write the electron configuration for the
phosphide ion?
CONDENSED ELECTRON CONFIGURATIONS
• There is a more shortened version for electron configuration, where the
is represented in square brackets and is followed by the remaining electrons in their
appropriate configuration. This is generally used for elements beyond
Example:
The electron configuration for Mg is 1s22s22p63s2
The condensed electron configuration for Mg is [Ne]3s2
Example 3: Write the condensed electron configuration for bromine?
.
ELECTRON CONFIGURATIONS AND TRANSITION METALS
• For transition metals, additional electrons begin to occupy the
. There are two
exceptions to the Aufbau principle:
and
. They prefer a low
energy half-filled 4s orbital.
• According to experimental evidence, it is more stable for electrons to have a low energy state
Element
Z
Electron Confign
Scandium
21
1s22s22p63s23p64s23d
Titanium
22
1s22s22p63s23p64s23d
Vanadium
23
1s22s22p63s23p64s23d
Chromium
24
Manganese
25
1s22s22p63s23p64s23d
Iron
26
1s22s22p63s23p64s23d
Cobalt
27
1s22s22p63s23p64s23d
Nickel
28
1s22s22p63s23p64s23d
Copper
29
Zinc
30
1s22s22p63s23p64s23d
Gallium
31
1s22s22p63s23p64s23d
Short Electron Confign
Important Points to Remember with Electron Configuration and the Periodic Table:
1. (n+1)s orbitals fill before nd orbitals. For example (3+1)s = 4s orbital fills before 3d orbitals
2. There are 14
elements. They correspond to the filling of the
orbitals. There are 14
elements. They correspond to the filling of the
orbitals
3. In certain cases, there is more stability with
within the lanthanides
and actinides
4. The atoms of every member element in each group have the
configuration (we usually do not count the d orbital electrons)
EXPLAINING IONIC CHARGES
What do we know about transition metals?
Example 4: What is the electron configuration of Cadmium? What is the electron configuration of
the cadmium ion (Cd2+)?
Cd:
Cd2+:
Example 5: What is the electron configuration of Lead? What are the multiple ions that lead can
form? What is the electron configuration of these ions?
Pb:
Pb Ion (
):
Pb Ion (
):
EXPLAINING MAGNETISM
Elements that are regarded as magnetic have the following properties:
• They generally tend to have
• Possess
(small dense packs of atoms) which align themselves randomly
(The atoms in a domain however are aligned in the same direction)
Magnetic Field Absent
Presence of a Magnetic
Field
FERROMAGNETISM
• A property that certain
elements possess
• An external magnet causes the
domains within a metal to align
in the _____________________.
They _______________________
when the magnet is removed.
This is a very strong magnet.
• Examples: __________________
PARAMAGNETISM
• A property caused by unpaired
electrons with the ___________
The spinning creates a _______
___________________________
• The property is discovered when
the element is brought close to
a strong magnetic field.
• They are ___________________
when the magnet is removed
• Examples: __________________
Homework: Read Pages 160-172
- Practice Questions #1-4 on Page 166
- Practice Questions #1-2 on Page 170
- Review Questions #1-10 on Page 172