Transcript Electron Configuration

Electron Configuration
How electrons are arranged
Or
Goodbye Bohr!
Quantum Mechanics
In quantum mechanics,
the electrons occupy specific energy
levels (as in Bohr's model) but they
also
exist
within
specific
probability volumes called orbitals
with specific orientations in space.
The electrons within each orbital
has a distinct spin.
Probability
Under this new model,
we cannot predict
exactly where an
electron is. Rather we
can say that electrons
are most likely found
within certain areas.
These are called
probability volumes
(note the volume: 3D)
1s
2s
3s
n = The principle quantum number
Describes the possible energy
levels (how close it is to the
nucleus) and pictorially it
describes the orbital size.
n = 1, 2, 3…. where an orbital with
the value of 2 is larger than an orbital
with the value of 1.
Quantum Mechanics
l = angular momentum quantum
number
Describes the "shape" of the orbital
and can have values from 0 to n - 1 for
each n.
orbital designation :
s
p
d
f
Quantum Mechanics
ml =
magnetic quantum number
Related to the orientation of an orbital
in space relative to the other orbitals
with the same l quantum numbers. It
can have values between l and - l .
So for s, only 1 orientation is possible
But for p, s orientations are possible
How many are possible for d? f?
Quantum Mechanics
ms =
spin quantum number
An electron has either +1/2 or -1/2 spin
values; sometimes referred to as spin up
and spin down.
These are arbitrary and are only used to
designate different “addresses” for the
electrons
What does the electron cloud
look like?
NOT
THIS!!!
More like this:
1S
2S
2Px
2py
2Pz
3S
Each orbital contains 2 electrons maximum,
with opposite spins
Electron Configuration
Electron configuration is a shorthand notation for
describing the arrangement of the electrons
about the nucleus.
General Format using the quantum numbers:
n = principle quantum number
enl
l = angular momentum quantum
number
RULES:
e- = number of electrons
1. Fill the lowest energy levels first.
Lowest 1s, 2s, 2p, 3s , 3p, 4s, 3d , 4p
2. No more than two electrons per orbital.
3. Ready for an easier way?
s
p
s
p
Least expensive rooms
d filled first
Two people perdroom
s
No one likes
p to share a room (only
d 1 bed)
s
People inpthe same bed sleep head
d to toe
s
INKEEPERS
RULES
p
s
House Model
6s
PRICES
36
6d
6p 6p 6p
5s
5p
4s
$
4p
3s
3p
2s
2p
1s
5p
5p
6d 6d 6d
5d 5d 5d 5d 5d
$$$
$$
4p
3p
2p
4p 4d 4d 4d 4d 4d
3p 3d 3d 3d 3d 3d
2p
House Model
6s
6p
5s
5p
4s
4p
3s
3p
2s
2p
1s
6p
5p
4p
3p
2p
36
6d
6d
6d
6d
6p
5p
5d 5d 5d 5d 5d
4p 4d 4d 4d 4d 4d
3p 3d 3d 3d 3d 3d
2p
House Model
Electron Configuration
Examples:
H:
1s1
He:
1s2
Li :
1s2 2s1
2 2s2 2p6 3s2 3p6 4s2 3d7
1s
Co:
2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
1s
Br:
red is valence electrons
why aren’t d valence?
The condensed electron configuration
distinguishes the core electrons from the
valence electrons.
CORE electrons are tightly held to the nucleus
and resemble a noble gas configuration.
VALENCE electrons are the outer most electrons
and are involved in chemical reactions.
Examples of the condensed configuration:
Li:[He] 2s1
Co:[Ar] 4s2 3d7
Br:[Ar] 4s2 3d10 4p5
10s
9s
8s
7s
9p
8p
7p
6p
8d
7f
7d
6f
5g
6d
5d
6s
5p
5s
4p
4s
3p
3s
2p
2s
1s
6g
5f
4f
4d
3d
But check out this
simple table at right. If
you draw diagonal
arrows
starting
at the
It shows
the precise
bottominlike
this…
order
which
the
energy levels are
arranged from lowest to
10s
9s
8s
7s
6s
5s
4s
3s
2s
1s
10p
9p
8p
7p
6p
5p
4p
3p
2p
10d
9d
8d
7d
6d
5d
4d
3d
10f
9f
8f
7f
6f
5f
4f
10g
9g
8g
7g
6g
5g
10h
9h
8h
7h
6h
So what does all this have to do with chemistry?
Below is a rough sketch of the periodic table. For the
sake of this discussion, we are going to move He over
so it is in that little open space next to H:
And now we are going to number the periods 1
through 7:
As you will see, these periods
s
1 2
correspond (more or less) to the
p
1 H
1 2 3 4
energy levels we’ve just been
2
discussing.
d
1 2 3 4 5 6 7 8 9 10
And we are going to designate the four 3
distinct rectangular blocks by the type 4
5
of sublevel they match up with: “s,”
6
“p,” “d” and “f:”
7
And let’s also number the groups
1 2 3 4 5 f6 7 8 9 10 11 12 13 14
within each block (1,2,3,4…)
Now let’s take the first ten sublevels (1s,
2s,
2p…) and see how the electrons filling
these
sublevels takes us row by row across the periodic table, and allows us to
read electron configurations right off the table…
He
5 6
4d
5s
4p
4s
s
3d
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
5 6
9 10
7 8 9 10 11 12 13 14
OK, so we’re going to use arrows pointing up or down to represent
the electrons. Can you guess into which box the first electron would
go given that it is attracted to the nucleus?
4d
5s
4p
4s
3d
s
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
5 6
9 10
7 8 9 10 11 12 13 14
That’s right: it goes in the 1s
1 sublevel. And its el. config is 1s2.
Notice in the table above where H is – in the area designated as 1s.
So where does the next electron go?
1s
4d
5s
4p
4s
3d
s
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
5 6
9 10
7 8 9 10 11 12 13 14
If you were thinking it went
2 in the 2s, then you forgot that each
orbital can hold up to two electrons. Note how He is right here in the
area designated as 1s2 and so its el. config. is 1s2.
1s
4d
5s
4p
4s
3d
s
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
5 6
9 10
7 8 9 10 11 12 13 14
Now that the 1s 2
is filled,1 the next electron goes in the next
sublevel – the 2s. Again note how Li is in 2s1.
Its full el. conf. is 1s2 2s1. What is Be’s el. conf?
1s 2s
4d
5s
4p
4s
3d
s
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
5 6
9 10
7 8 9 10 11 12 13 14
Now that the 1s 2
is filled,1 the next electron goes in the next
sublevel – the 2s. Again note how Li is in 2s1.
Its full el. conf. is 1s2 2s1. What is Be’s el. conf?
1s 2s
4d
5s
4p
4s
s
3d
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
5 6
9 10
7 8 9 10 11 12 13 14
Is this2what you
Notice how B is in
2 were1thinking?
1
the 2p spot.
1s 2s 2p
So its full el. conf. is 1s2 2s2 2p1. What’s next?
4d
5s
4p
4s
s
3d
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
5 6
9 10
7 8 9 10 11 12 13 14
Is this2what you
C is in
2 were2thinking? Notice2 how
2
2
the 2p spot. So its el. conf. is 1s 2s 2p2
1s 2s 2p
Notice also how when we fill a sublevel…
4d
5s
4p
4s
s
3d
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
9 10
7 8 9 10 11 12 13 14
…we
2 put one
2 electron
3 in each orbital until the
sublevel is half filled…
1s 2s 2p
5 6
4d
5s
4p
4s
s
3d
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
9 10
7 8 9 10 11 12 13 14
…2and then
2 we go4back and start pairing off
1s 2s 2p
5 6
This is called “Hund’s Rule, but it also referred to as
the bus seat rule. Can you figure out why?
4d
5s
4p
4s
s
3d
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
5 6
9 10
7 8 9 10 11 12 13 14
Look2at F. It’s
2 just one
5 electron away from having
filled 2p sublevel…
1s 2s 2p
And it’s just one square away from the end of the 2p block.
4d
5s
4p
4s
s
3d
1 2
3p
3s
2p
2s
1
2
3
4
5
6
7
1 2
d
1 2 3 4 5 6
f
1 2 3 4 5 6
1s
+
7 8
p3 4
5 6
9 10
7 8 9 10 11 12 13 14
And then
filled outer level. Na is
2 Ne has
2 a completely
6
next. Can you guess where the next electron is going
to go?
1s 2s 2p
For example, Cl (#17) which is right here on the table:
So the answer would be 1s2 2s2 2p6 3s2 3p5
The short cut would be: [Ne]3s2 3p5
1
2
3
4
5
6
7
1s
2
2s
2
3s
2
2p
6
3p
5
Orbital Diagrams
Orbital diagrams are written in order of increasing energy
levels starting with the lowest energy level the 1s orbital.
___
___
___
___
___
___
___
___
___ ___ 4p
___ ___ ___ ___ 3d
4s
___ ___ 3p
3s
___ ___ 2p
2s
Remember the order!!
1s
RULES:
(1) fill the lowest
energy level first
(2) fill each orbital in
a subshell with one
electron first before
you double up.
(3) Completely fill
each subshell before
proceeding to the
next energy level.
Orbital Diagrams
Practice Problems
1. Fill in the orbital diagrams for:
C
O
Ne
Na
___ ___ ___ 4p
__ __ __ __ __ 3d
___ 4s
___ ___ ___ 3p
___ 3s
___ ___ ___ 2p
___ 2s
___ 1s
Si
Cl
Ar
K
___ ___ ___ 4p
__ __ __ __ __ 3d
___ 4s
___ ___ ___ 3p
___ 3s
___ ___ ___ 2p
___ 2s
___ 1s
Orbital Diagrams
Practice Problem Answers
Fill in the orbital diagrams for:
C
___ ___ ___ 4p
__ __ __ __ __ 3d
___ 4s
___ ___ ___ 3p
___ 3s
___ ___ ___ 2p
___ 2s
___ 1s
O
___ ___ ___ 4p
__ __ __ __ __ 3d
___ 4s
___ ___ ___ 3p
___ 3s
___ ___ ___ 2p
___ 2s
___ 1s
Orbital Diagrams
Practice Problem Answers
Fill in the orbital diagrams for:
Ne
Na
___ ___ ___ 4p
__ __ __ __ __ 3d
___ 4s
___ ___ ___ 3p
___ 3s
___ ___ ___ 2p
___ 2s
___ 1s
___ ___ ___ 4p
__ __ __ __ __ 3d
___ 4s
___ ___ ___ 3p
___ 3s
___ ___ ___ 2p
___ 2s
___ 1s
Orbital Diagrams
Practice Problem Answers
Fill in the orbital diagrams for:
Si
Cl
___ ___ ___ 4p
__ __ __ __ __ 3d
___ 4s
___ ___ ___ 3p
___ 3s
___ ___ ___ 2p
___ 2s
___ 1s
___ ___ ___ 4p
__ __ __ __ __ 3d
___ 4s
___ ___ ___ 3p
___ 3s
___ ___ ___ 2p
___ 2s
___ 1s