Electron Configuration
Filling of atomic orbital's and energy
levels
Electron Configuration
• A form of notation which shows how the
electrons are distributed among the various
atomic orbital and energy levels.
• The format consists of a series of numbers,
letters and superscripts as shown below
He
2
1s
Information Provided by Electron
Configuration - Example He - 1s2
• The large number "1“ in the example, stands for
the energy level (refers to the principle quantum number "n" ).
– It tells us that the electrons of helium occupy the first
energy level of the atom.
• The letter "s” tells us that the electrons of the
helium element occupy an "s" or spherical orbital
• The exponent "2“ in the example, refers to the
total number of electrons in that orbital or subshell.
– There are two electrons in the spherical orbital at the
first energy level.
Information Needed to Understand
Electron Configurations!
• The number of sublevels that an energy level can
contain is equal to the principle quantum number
of that level (n).
– For example, the second energy level has two
sublevels
– The third energy level has three sublevels.
– Names of Sublevels
•
•
•
•
The first sublevel is called an s sublevel.
The second sublevel is called a p sublevel.
The third sublevel is called a d sublevel
The fourth sublevel is called an f sublevel.
f
d
p
S
Check Your Progress!
1. How many sublevels are in the first energy
level?
2. How many sublevels are in the fourth energy
level?
3. What energy level has 3 sublevels?
4. What energy level has 2 sublevels?
Answers
1.
2.
3.
4.
One
Four
Third energy level
The second energy level
Sublevels and Orbitals
• An orbital is a space that can be occupied by up
to two electrons.
• Each type of sublevel holds a different number
of orbitals, and therefore, a different number of
electrons.
– s sublevels have 1 orbital, which can hold up to two
electrons.
– p sublevels have 3 orbitals, each of which can hold 2
electrons, for a total of 6 electrons.
– d sublevels have 5 orbitals, for a possible total of 10
electrons.
– f sublevels, with 7 orbitals, can hold up to 14
electrons.
Electron Capacity of Sublevels
Orbital and Electron Capacity for the Four Named Sublevels
Sublevel
# of Orbitals
Maximum # of Electrons
s
1
1 x 2=
2
p
3
3 x 2=
6
d
5
5 x 2=
10
f
7
7 x 2=
14
Total Number of Orbital and Electrons
per Energy Level
• An easy way to calculate the number of
orbitals found in an energy level is to
use the formula n2. (n=the energy level)
– For example, the third energy level (n=3) has a
total of 32, or nine orbitals.
– This makes sense because we know that the third
energy level would have 3 sublevels;
• an s sublevel with 1 orbital, a p sublevel with 3 orbitals
and a d sublevel with 5 orbitals. 1 + 3 + 5 = 9, so the
formula n2 works!
Lets check your progress again!
• How many orbitals are found in the fourth
energy level?
• Which sublevels will it have?
• How many orbitals are in each of the
sublevels?
Answers
•
•
•
•
•
•
n=4
N2 , 42 or 16 orbitals!
an s sublevel with one orbital
a p sublevel with 3 orbitals
a d sublevel with 5 orbitals.
An f sublevel with 7 orbitals
Total Number of Electrons per Energy
Level
• An easy way to calculate the total number of
electrons that can be held by a given energy
level is to use the formula 2n2.
– For example, the fourth energy level (n=4) can hold
2(4)2 = 32 electrons.
– This makes sense because the fourth energy level would
have four sublevels, one of each of the named types.
• The s sublevel hold 2 electrons,
• the p sublevel holds 6 electrons ,
• the d sublevel holds 10 electrons and the f sublevel holds 14
electrons.
• 2 + 6 + 10 + 14 = 32, so the formula 2n2 works!
Lets check your progress
• How many electrons can the third energy level
hold?
• How do you know?
Answer
• the third energy level (n=3) can
hold 2(3)2 = 18 electrons.
– This makes sense because the third energy level
would have three sublevels, one of each of the
named types.
•
•
•
•
The s sublevel hold 2 electrons,
the p sublevel holds 6 electrons ,
the d sublevel holds 10 electrons
2 + 6 + 10 = 18, so the formula 2n2 works!
Electron Capacity of the First 4 Energy
Levels
Orbitals and Electron Capacity of the First Four Principle Energy Levels
Principle
Type of
energy level (n) sublevel
Number of
orbitals per
type
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
Number of
orbitals per
level(n2)
Maximum
number of
electrons (2n2)
Different Shapes of Orbitals
Order of Filling Sublevels with
Electrons
• The energy sublevels are filled in a specific
order
• You must follow the rules to understand when
electrons will fill each level
• Once you know this you can write them out in
electron configuration
Start at the beginning of each arrow
then follow it all of the way to the end,
filling in the sublevels that it passes
through
Check up from the neck up!
• What is the order in which sublevels are filled
by electrons?
– Please write it out through the seventh energy
level!
– Hint!!!! --- draw the diagram first then use it!
Look carefully at the order!
• the order for filling in the sublevels becomes;
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f,
5d, 6p, 7s, 5f, 6d,7p.
Remember!
• How many electrons do each of these energy
levels hold?
• S holds 2
• P holds 6
• D holds 10
• F holds 14
Orbital and Electron Capacity for the Four
Named Sublevels
Sublevel
# of Orbitals
Maximum # of Electrons
s
1
1 x 2=
2
p
3
3 x 2=
6
d
5
5 x 2=
10
f
7
7 x 2=
14
Write electron configurations for each
of these elements
1. K
2. Ag
3. C
Answer
1 K has 19 electrons- 1s22s22p63s23p64s1
• (S holds 2, P holds 6)
2 Ag has 47 electrons- 1s2 2s2 2p6 3s2 3p6 4s2
3d10 4p6 5s1 4d10
(to make it neater we write the energy levels together like this1s2 2s2p6 3s2p6d10 4s2p6d10 5s1 )
3 C has 6 electrons- 1s2 2s2 2p2