Quantum Mechanical Model
and Electron Configurations
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. (Erwin Schrodinger)
5.1
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.
5.1
Atomic Orbitals

Different atomic orbitals are denoted by letters.
The s orbitals are spherical, and p orbitals are
dumbbell-shaped.
5.1
Atomic Orbitals

Four of the five d orbitals have the same shape
but different orientations in space.
5.1
Atomic Orbitals

The numbers and kinds of atomic orbitals depend
on the energy sublevel.
Number of Orbitals in Each
Sublevel
Sublevel
Number of
Orbitals
Number of
Electrons in
each Orbital
Number of
Electrons in
Each Sublevel
s
1
2
2
p
3
2
6
d
5
2
10
f
7
2
14
5.2
Electron Configurations

Electron Configurations

What are the three rules for writing the electron
configurations of elements?
5.2
Electron Arrangement in
Atoms
>
Electron Configurations
Aufbau Principle
According to the aufbau principle, electrons
occupy the orbitals of lowest energy first. In the
aufbau diagram below, each box represents an
atomic orbital.
Slide
9 of 20
© Copyright Pearson Prentice Hall
5.2
Electron Arrangement in
Atoms
>
Electron Configurations
Pauli Exclusion Principle
According to the Pauli exclusion principle, an
atomic orbital may describe at most two
electrons. To occupy the same orbital, two
electrons must have opposite spins; that is, the
electron spins must be paired.
Slide
10 of 20
© Copyright Pearson Prentice Hall
5.2
Electron Arrangement in
Atoms
>
Electron Configurations
Hund’s Rule
Hund’s rule states that electrons occupy orbitals
of the same energy in a way that makes the
number of electrons with the same spin direction
as large as possible.
Slide
11 of 20
© Copyright Pearson Prentice Hall
Electron Arrangement in
Atoms
>
Slide
12 of 20
© Copyright Pearson Prentice Hall
Electron Arrangement in
Atoms
>
Slide
13 of 20
© Copyright Pearson Prentice Hall
Use each
type of
diagram to
write out
configuration.
Slide
14 of 20
© Copyright Pearson Prentice Hall
for Conceptual Problem 1.1
DO SHORT HAND AND ORBITAL DIAGRAM
Problem Solving 5.9 Solve Problem 9
with the help of an interactive guided
tutorial.
Ions: Cation Vs. Anion

Ion: an atom or molecule with a net electric
charge due to the loss or gain of one or
more electrons.

Cation: Positively Charged Ion


Loses Electrons
Anion: Negatively Charged Ion

Gains Electrons
Ion Electron Configurations

What charges do elements tend to have to
be stable?

GET OUT PERSONAL PERIODIC TABLES
Charges for Groups 1, 2, 15, 16, 17, 18

Octet Rule and Valence
Electrons



Atoms follow the octet rule because they
always seek the most stable electron
configuration.
Valence Electrons: Electrons in outermost
shell. How do we find them?
Octet = 8

Elements want to have 8 electrons in their outer
shell…
Practice: Electron Configuration
of Ions




Cl-1
O-2
Na+1
Ca+2
Do short hand and orbital diagram.
Weird Stuff

http://www.newscientist.com/blogs/nstv/20
11/09/one-minute-physics-isschrodingers-cat-dead-or-alive.html
END OF SHOW