Transcript Electrons

ELECTRON ORBITALS
Cartoon courtesy of lab-initio.com
THE BOHR MODEL OF THE ATOM
I pictured electrons
orbiting the nucleus much
like planets orbiting the
sun.
But I was wrong! They’re
more like bees around a
hive.
Neils Bohr
QUANTUM MECHANICAL
MODEL OF THE ATOM
Mathematical laws can identify the
regions outside of the nucleus
where electrons are most likely to
be found.
These laws are beyond the scope of
this class…
HEISENBERG UNCERTAINTY PRINCIPLE
“One cannot simultaneously
determine both the position
and momentum of an electron.”
You can find out where the
electron is, but not where it
is going.
Werner
Heisenberg
OR…
You can find out where the
electron is going, but not
where it is!
QUANTUM NUMBERS
Numbers that specify the properties of atomic
orbitals and electrons.
 They indicate the region occupied by an orbital
in terms of:

1.
2.
3.
Distance from the nucleus
Orbital shape
Position with respect to the 3-D x, y, z axis
ELECTRON ENERGY LEVEL (SHELL)
Generally symbolized
by n, it denotes the
probable distance of
the electron from
the nucleus. “n” is
also known as the
Principle Quantum
number.
As “n” increases the
radius increases.
ORBITAL QUNATUM NUMBER (SUBSHELL)

Generally symbolized by l, it is a measure
of orbital angular momentum, which
indicates the shape of the orbital.
MAGNETIC QUANTUM NUMBER

Generally symbolized by ml, in indicates
the orbital around the 3 axes in space
(orientation in space)
s
= 1 orientation
 p = 3 orientations
 d = 5 orientations
 f = 7 orientations

Identifies the specific orbital.
SPIN QUANTUM NUMBER
Generally symbolized by ms, it tells the
electrons spin on its axis.
 Clockwise or counterclockwise
 Whether bound or free all electrons spin.

Electron Orbitals
AN ORBITAL IS A REGION WITHIN AN
ENERGY LEVEL WHERE THERE IS A
PROBABILITY OF FINDING AN ELECTRON.
Orbital shapes are defined as the surface
that contains 90% of the total electron
probability.
There are four shapes or
sublevels:
s
p
d
f
Each sublevel has
“orientations” or
orbitals around the
origin of the x-y-z
axis.
Take a look!
S ORBITAL SHAPE
The s orbital has
a spherical shape
centered around
the origin of the
three axes in
space.
S
=
Shaped like a sphere
1) No matter which way you turn it in
space, it will always be a sphere so
there are no separate orbitals
(orientations in space).
X
Z
Y
Z
Y
X
1s Z
2s
3s
Y
X
Again,
Still aa
sphere!
sphere!
2) It exists on every energy level.
Level 2’s S sublevel is big enough to
encompass Level 1’s and Level 3’s
encompasses them both, like nesting
dolls.
3) No matter how big ‘s’ is, it only can
hold 2 electrons, max!
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.
P
= Dumb Bell shape
1) The ‘p’ sublevel is made up of 3
2e-
orbitals or ‘orientations’ in space.
Y
2e
- Z
2eX
px When it lies along the x-axis
py When it lies along the y-axis
pz When it lies along the z-axis
2) Each orientation or orbital can hold 2
electrons max for a total of 6 electrons.
3) The ‘p’ sublevel is first found on Principle
Energy Level 2. Like ‘s’, it increases in
size with each increase in energy level.
D ORBITAL SHAPES
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
ENERGY LEVELS, ORBITALS, ELECTRONS
Energy
Level
(n )
Orbital type
in the
energy level
(types = n)
Number of
orbitals
Number of
Electrons
Number of
electrons per
Energy level
(2n2)
1
s
1
2
2
2
s
p
1
3
2
6
8
3
s
p
d
1
3
5
2
6
10
18
4
s
p
d
f
1
3
5
7
2
6
10
14
32
ORBITAL FILLING TABLE
ELECTRON CONFIGURATION OF THE
ELEMENTS OF THE FIRST THREE SERIES
How does this work,
anyway?
Each element can be represented by its
**Electron Configuration**
for example: The superscript tells how many
electrons are in that sublevel.
Carbon (C) is 1s2 2s2 2p2
The coefficient shows what level from
The letter s,p,d or f, represents the shape of the
the nucleus.
is known
the Quantum
sublevel.
This isThis
known
as theas
Orbital
Principle Quantum Number.
Number.
So
There are 4 electrons total in
the valence shell. These are
the valence electrons.
1s22s22p2
tells us that Carbon has:
2 2
2 electrons in the ‘s’
sublevel (the sphere) on
principle energy level ‘1’
The outermost energy
level is ‘2’ for Carbon.
This is its valence shell.
2 electrons in the ‘s’
sublevel (the sphere) on
principle energy level ‘2’
2 electrons in the ‘p’ sublevel
(the dumb bell) on principle
energy level ‘2’
•STUDY for the PT QUIZ (all required elements)
Creating Electron Configurations
It starts with the
periodic table:
The transition
metals are
known as the
“d” block
The right side
is known as
the “p” block
The first two
columns, and
“He” are
called the “s”
bock.
The bottom two rows, called the rare earth
elements or Lanthanide and Actinide series
make up the “f” block.
ELECTRON SPIN
Electron spin describes the behavior
(direction of spin) of an electron
within a magnetic field.
Possibilities for electron spin:
1

2
Clockwise
1

2
Counterclockwise
PAULI EXCLUSION PRINCIPLE
Two electrons occupying
the same orbital must
have opposite spins
Wolfgang
Pauli
A. GENERAL RULES

Pauli Exclusion Principle
 Each
orbital can hold TWO electrons with
opposite spins.
2
P’s in a Pod
A. GENERAL RULES

Aufbau Principle
 Electrons
fill the
lowest energy
orbitals first.
 “Lazy
Rule”
Tenant
U
ufBA
a
A. GENERAL RULES

Hund’s Rule
 Within
a sublevel, place one e- per orbital before
pairing them.
 “Empty
Bus Seat Rule” or Hand’s Rule
WRONG
RIGHT
___
4p
___
3d
___
4s
___
3p
___
3s
___
2p
___
2s
___
1s
___
___
___
___
EXAMPLE 1
___
___

___
___
___
___
Example of Si, Z=14
*Hint #1: The “Z” number
refers to the Atomic
Number which is the
number of protons AS
WELL AS electrons.
2
2
6
2
2
1s 2s 2p 3s 3p
___
4p
___
3d
___
4s
___
3p
___
3s
___
2p
___
2s
___
1s
___
___
___
___
___
EXAMPLE 2YOU TRY
___

___
___
___
___
2
Example of Ti, Z=22
*Hint #1: The “Z” number
refers to the Atomic
Number which is the
number of protons AS
WELL AS electrons.
2
6
2
6
2
2
1s 2s 2p 3s 3p 4s 3d
YOU TRY THESE

Mg
2
2
6
2
1s 2s 2p 3s
2
2
6
2
5

Cl
1s 2s 2p 3s 3p

Co
1s2 2s2 2p6 3s2 3p6 4s2 3d7

Br
2
2
6
2
6
2
10
1s 2s 2p 3s 3p 4s 3d 4p
5
BUILDING AN ELECTRON CONFIGURATION
Principle Energy Level
(click the mouse to start an example)
4
4s
3px
3py
3pz
4d
4d
4d
3d
3d
4d
4d
3
3s
3px
3py
3pz
2
2s
2px
1s
1s2 2s2 2p4
1
nucleus
2py
2pz
3d
O
Z=8
3d
3d
BUILDING AN ELECTRON CONFIGURATION
Principle Energy Level
(click the mouse to start an example)
4
4s
3px
3py
3pz
4d
4d
4d
3d
3d
4d
4d
3
3s
3px
3py
3pz
2
2s
2px
1s
1s2 2s2 2p6
1
nucleus
2py
2pz
3d
3d
Ne
Z=10
3d
BUILDING AN ELECTRON CONFIGURATION
Principle Energy Level
(click the mouse to start an example)
4
4s
3px
3py
3pz
4d
4d
4d
3d
3d
4d
4d
3
3s
3px
3py
3pz
3d
2
2s
1
1s
nucleus
2px
2py
2pz
1s2 2s2 2p6 3s2 3p3
2+ 2 + 6 + 2 + 3 =
3d
3d
P
Z=15
15
Principle Energy Level
BUILDING AN ELECTRON
CONFIGURATION
(click the mouse to start an example)
4
4s
3
3s
3px
3px
3py
3py
3pz
3pz
4d
3d
4d
4d
3d
3d
4d
3d
2s
1
1s
1s2
2py
2
2s
2pz
2
6
2p 3s
3d
K
2
2px
4d
3p6 4s1
nucleus
2+ 2 + 6 + 2 + 6
+1 =
Z=19
19
Element
Lithium
Configuration
notation
Orbital notation
1s22s1
[He]2s1
____
1s
Beryllium
____
____
2p
____
____
2s
____
____
2p
____
[He]2s2p2
____
2s
____
____
2p
____
1s22s22p3
[He]2s2p3
____
2s
____
____
2p
____
1s22s22p4
[He]2s2p4
____
2s
____
____
2p
____
1s22s22p5
[He]2s2p5
____
1s
Neon
____
2s
1s22s22p2
____
1s
Fluorine
____
[He]2s2p1
____
1s
Oxygen
____
2p
1s22s22p1
____
1s
Nitrogen
____
[He]2s2
____
1s
Carbon
____
2s
1s22s2
____
1s
Boron
Noble gas
notation
____
2s
____
____
2p
____
1s22s22p6
[He]2s2p6
____
1s
____
2s
____
____
2p
____
ANALOGY
Electron Cloud = dorm
•Energy level (shell) = floor
•Subshell = room
•Orbital = love seat
•Spin = each person