Transcript Electron Configuration Notes

Electrons
Configurations
Cartoon courtesy of NearingZero.net
Wave-Particle Duality
JJ Thomson won the Nobel prize for describing the
electron as a particle.
His son, George Thomson won the Nobel prize for
describing the wave-like nature of the electron.
The
electron is
a particle!
The
electron is
an energy
wave!
The Wave-like Electron
The electron propagates
through space as an energy
wave. To understand the
atom, one must understand
the behavior of
electromagnetic waves.
Louis deBroglie
Spectroscopic analysis of the visible
spectrum…
…produces all of the colors in a continuous spectrum
Electron
transitions
involve jumps
of
definite
amounts of
energy.
This produces bands
of light with definite
wavelengths.
Quantum Numbers
Each electron in an atom has a unique set of 4
quantum numbers which describe it.




Principal quantum number
Angular momentum quantum number
Magnetic quantum number
Spin quantum number
Pauli Exclusion Principle
No two electrons in an atom
can have the same four
quantum numbers.
Wolfgang
Pauli
Principal Quantum Number
Generally symbolized by n, it denotes the shell
(energy level) in which the electron is located.
Number of electrons
that can fit in a shell:
2n2
Angular Momentum
Quantum Number
The angular momentum quantum number, generally
symbolized by l, denotes the orbital (subshell) in
which the electron is located.
Magnetic Quantum Number
The magnetic quantum number, generally
symbolized by m, denotes the orientation of the
electron’s orbital with respect to the three axes in
space.
Assigning the Numbers
 The three quantum numbers (n, l, and m) are
integers.
 The principal quantum number (n) cannot be
zero.
 n must be 1, 2, 3, etc.
 The angular momentum quantum number (l) can
be any integer between 0 and n - 1.
 For n = 3, l can be either 0, 1, or 2.
 The magnetic quantum number (m) can be any
integer between -l and +l.
 For l = 2, m can be either -2, -1, 0, +1, or
+2.
Spin Quantum Number
Spin quantum number denotes the behavior
(direction of spin) of an electron within a magnetic
field.
Possibilities for electron spin:
1

2
1

2
Uncertainty Principle
 In
1927 by Werner Heisenberg
(German theoretical physicist)
 electrons
can only be detected by their
interaction with light
 any
attempt to locate a specific
electron knocks the electron off
course
Uncertainty Principle
 Heisenberg
Uncertainty Principle- it is
impossible to know both the position
and velocity of an electron
 We
can find the most likely position of
an electron
Orbitals
 each
sublevel is broken into orbitals
 each orbital can hold a maximum of 2
electrons
 orbital-
a 3D region around the
nucleus that has a high probability of
holding electrons
An orbital is a region within an atom where there
is a probability of finding an electron. This is a
probability diagram for the s orbital in the first
energy level…
Orbital shapes are defined as the surface that
contains 90% of the total electron probability.
Sizes of s orbitals
Orbitals of the same shape (s, for instance) grow
larger as n increases…
Nodes are regions of low probability within an
orbital.
The s orbital has a spherical shape centered around
the origin of the three axes in space.
s orbital shape
P orbital shape
There are three dumbbell-shaped p orbitals in
each energy level above n = 1, each assigned to
its own axis (x, y and z) in space.
Things get a bit more
complicated with the five d
orbitals that are found in
the d sublevels beginning
with n = 3. To remember
the shapes, think of “double
dumbells”
…and a
“dumbell
with a donut”!
Shape of f orbitals
Number of Orbitals
sublevel
s
p
d
f
max # e2
6
10
14
# orbitals
1
3
5
7
Energy
Level
1
2
3
4
Number of
Sublevels
1
2
3
4
Types of
Sublevels
s
s,p
s,p,d
s,p,d,f
Energy Sublevels
#
Total
Total
Level
Orbitals Orbitals Electrons
1
2
3
4
Energy Sublevels
#
Total
Total
Level
Orbitals Orbitals Electrons
1
s
1
1
2
2
s
1
4
8
p
3
s
1
9
18
p
3
d
5
s
1
16
32
p
3
d
5
f
7
3
4
Orbital filling table
Electron configuration of the
elements of the first three series
Irregular confirmations of Cr and
Cu
Chromium steals a 4s electron to half
fill its 3d sublevel
Copper steals a 4s electron to FILL
its 3d sublevel
Electron Configurations
 the
arrangement of electrons in an atom
 each type of atom has a unique electron
configuration
 electrons tend to assume positions that
create the lowest possible energy for
atom
 ground state electron configurationlowest energy arrangement of electrons
Rules for Arrangements

Aufbau Principle- an
electron occupies the
lowest-energy orbital
that can receive it

Beginning in the 3rd
energy level, the
energies of the
sublevels in different
energy levels begin to
overlap
Rules for Arrangements
 Pauli
Exclusion Principle- no two
electrons in the same atom can have
the same set of 4 quantum numbers
 Hund’s Rule- orbitals of equal energy
are each occupied by one electron
before any orbital is occupied by a
second
 all unpaired electrons must have the
same spin
Rules for Arrangements
Writing Configurations
 Orbital



Notation:
an orbital is written as a line
each orbital has a name written below it
electrons are drawn as arrows (up and
down)
 Electron

Configuration Notation
number of electrons in sublevel is added
as a superscript
Order for Filling Sublevels
Writing Configurations
Start by finding the number of electrons in
the atom
 Identify the sublevel that the last electron
added is in by looking at the location in
periodic table
 Draw out lines for each orbital beginning
with 1s and ending with the sublevel
identified
 Add arrows individually to the orbitals until
all electrons have been drawn

Silicon
number of electrons: 14
 last electron is in sublevel: 3p

1s
2s
2p
3s
3p
Valence Electrons- the electrons in the outermost
energy level
Chlorine
number of electrons: 17
 last electron is in sublevel: 3p

1s
2s
2p
3s
3p
Sodium
number of electrons: 11
 last electron is in sublevel: 3s

1s
2s
1s2 2s2 2p6 3s1
2p
3s
Calcium
number of electrons: 20
 last electron is in sublevel: 4s

1s
2s
3p
2p
4s
1s2 2s2 2p6 3s2 3p6 4s2
3s
Bromine
number of electrons: 35
 last electron is in sublevel: 4p

1s
4s
2s
2p
3d
3s
3p
4p
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
Argon
number of electrons: 18
 last electron is in sublevel: 3p

1s
2s
2p
1s2 2s2 2p6 3s2 3p6
3s
3p
Noble Gas Notation
short hand for larger atoms
 configuration for the last noble gas is
abbreviated by the noble gas’s symbol in
brackets
