This document discusses electron configurations and orbital diagrams. It begins by defining atomic orbitals as regions where electrons are likely to be found, and notes that electron configurations show how electrons are arranged around the nucleus for each element. It then explains the four quantum numbers - principal, angular momentum, magnetic, and spin - that describe electrons and their locations. The document provides examples of writing electron configurations and constructing orbital diagrams according to Aufbau principle, Pauli exclusion principle, and Hund's rule.

1. Electron Configurations and
Orbital Diagrams
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MIZZZ FOSTER © 2015

2. Atomic orbitals
 Atomic orbitals are the region of space in which
there is a high probability of finding the electron.
 In learning about electron configuration, you will
learn the actual pathways and arrangement of
electrons.
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3. Electron Configuration
 Electron configuration:
 shows how electrons are arranged around the nucleus.
 is unique to each element.
 allows us to predict chemical and bonding behaviors.
 Example:
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4. Quantum numbers
 Quantum numbers describe electrons.
 There are four quantum numbers:
1. Principle Quantum number : n
2. Secondary Quantum number: l
3. Magnetic Quantum number: ml
4. Spin Magnetic number: ms
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Tell us which
orbital the
electron is in.
Used for
writing electron
configurations

5. Principle quantum number : n
 The Principle Quantum
Number (n) is the
electron shell which
coincides with the
Period (row) of the
Periodic Table.
 The principle quantum
number determines the
size of the atomic orbital.
 The higher the value of n
the larger the atomic
orbital.
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PERIOD n
1 1
2 2
3 3
4 4
5 5
6 6
7 7
When orbitals have the same “n”
they are said to occupy the same
shell.

6. Principal quantum number : n 6

7. Secondary (Subshell)
Quantum number: l
 The Secondary Quantum
Number divides the shell
into subshells.
 The values of l have letter
designations and specific
electron cloud shapes.
 The letter designation is to
avoid confusion with the
principal quantum number.
 The value of l is determined
by l=n-1 .
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l 0 1 2 3
Letter s p d f
Max
electrons
2 6 10 14

8. Magnetic Quantum number: ml 8
 The magnetic quantum splits the subshells into individual orbitals based on their
orientation in space, n value, l value and shape.
 Each individual orbital holds 2 electrons.
 The number of orbitals per subshell is determined by 2l + 1 = ml and remember to
determine l the formula is n-1 = l .
n l ml #
orbitals
Orbital
name
#
electrons
1 0 0 1 1s 2
2 0 0 1 2s 2
2 1 -1 , 0 , +1 3 2p 6
3 0 0 1 3s 2
3 3p
3 3d
4 4s

9. Quantum Number
Interdependence
 Continue filling in the chart . . .
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n l ml #
orbitals
Orbital
name
#
electrons
1 0 0 1 1s 2
2 0 0 1 2s 2
2 1 -1 , 0 , +1 3 2p 6
3 0 0 1 3s 2
3 1 -1, 0, +1 3 3p 6
3 3d
4 4s
4 4p
4 4d
4 4f

10. Quantum Number
Interdependence
 If you used the formulas correctly your table should look like this…
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n l ml #
orbitals
Orbital
name
#
electrons
1 0 0 1 1s 2
2 0 0 1 2s 2
2 1 -1 , 0 , +1 3 2p 6
3 0 0 1 3s 2
3 1 -1, 0, +1 3 3p 6
3 2 -2 , -1, 0, +1, +2 5 3d 10
4 0 0 1 4s 2
4 1 -1, 0, +1 3 4p 6
4 2 -2 , -1, 0, +1, +2 5 4d 10
4 3 -3, -2 , -1 , 0, +1, +2, +3 7 4f 14

11. Periodic Table:
Secondary Quantum Locations
 The Periodic Table shows the Secondary Quantum Locations in blocks.
 Do not assume that the elements found in the specific blocks ONLY contain these
subshell shapes. That is NOT the case. This graphic is showing you where the subshells
BEGIN.
 As you can see the s block is always at the beginning of a period, followed by the d and
finally p. It is not until Period 6 and 7 that f block shows up.
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12. Spin Magnetic Quantum
 The fourth number (ms) specifies how many electrons can
occupy that orbital and is used for electron spin.
 Example: +1/2 = spin up; -1/2 = spin down
 This quantum number is only used in orbital diagrams.
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13. Reading the
Electron Configuration
 When reading an electron configuration
keep these four things in mind. . .
 the number indicates the shell number (Period,
energy level)
 the letter indicates the sub-shell within the
shell (shape).
 the superscript indicates the number of
electrons in the sub-shell (s = 2, p = 6, d = 10,
f = 14)
 Ml indicates how many orbitals you will have
for each shell (Period, energy level.)
 When you add the superscript numbers
together you should get the total number of
electrons for that specific atom.
 Example: carbon has six electrons and its
electron configuration is 1s22s22p2
 2 +2 +2 =6 total electrons
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14. Writing the
Electron Configuration
 When writing an electron configuration keep
these SAME four things in mind. . .
 the number indicates the shell number (Period,
energy level)
 the letter indicates the sub-shell within the
shell (shape).
 the superscript indicates the number of
electrons in the sub-shell (s = 2, p = 6, d = 10,
f = 14).
 Ml indicates how many orbitals you will
have for each shell (Period, energy level.)
 When you write the electron
configuration you always start at 1s and
fill each shell before moving unto the
next. Use the fill order graphic to guide
you.
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15. Writing the
Electron Configuration
This is how you follow the fill diagram.
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16. Writing Electron Configuration using
the Periodic Table
 The periodic table can be used to find the electron configuration for an element
 First find the element on the periodic table
 Then follow through each element block in order by stating the energy level,
the orbital type, and the number of electrons per orbital type until you arrive
at the element.
 ALWAYS START AT HYDROGEN!
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17. Orbital Diagrams:
Mapping the electrons
17
ENERGY
INCREASES

18. Writing the
Electron Configuration
Lets try to write the electron configurations
for the following elements. Remember to fill
the orbital before proceeding to the next.
Use the atomic number of the element for
the number of electrons.
(s = 2, p = 6, d = 10, f = 14)
H =
He =
Li =
Be =
B =
C =
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19. Writing the
Electron Configuration
Are these the answers you wrote down?
H = 1s1
He = 1s2
Li = 1s2 2s1
Be = 1s2 2s2
B = 1s2 2s2 2p1
C = 1s2 2s2 2p2
GREAT JOB!!!
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20. Practice
 Draw the following elements’ orbital diagrams and
electron configurations.
 K, Potassium
 Kr, Krypton
 Pb, Lead
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21. Practice
 Answers
 K, Potassium
1s22s22p63s23p64s1
 Kr, Krypton
1s22s22p63s23p64s23d104p6
 Pb, Lead
1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p2
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22. Noble Gas configuration
 To write a noble gas (shorthand) configuration for any element,
count backwards from that element until you reach a noble gas.
 Write that element in brackets.
 Then, continue forward with next sub-shell(s) - see the
following version of the periodic chart that shows the sub-shell
order with respect to the elements.
 For example C = 1s2 2s2 2p2
 Carbon’s Noble Gas Configuration is = [He] 2s2 2p3
 It may not seem like a big difference but when you work with
elements of higher atomic numbers it is a great time saver when
writing out their configuration.
 For example Br = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
 The Noble Gas configuration of bromine is = [Ar]4s2 3d10 4p5
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23. Noble Gas configuration
 For example, if we wanted to do the shorthand
configuration for sodium (Na), you would count back
one element to neon (Ne) and put Ne in brackets.
 [Ne]
 Put this element symbol in brackets and then, noting
that the next correct sub-shell is 3s, include the rest of
the electrons as we did with the smaller elements.
 [Ne]3s1
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24. Practice
 Write the following noble gas configuration for the
following elements.
 Be, Beryllium
 F, Fluorine
 Ba, Barium
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25. Practice
 Write the following noble gas configuration for the
following elements.
 Be, Beryllium
 [He]2s2
 F, Fluorine
 [He]2s22p5
 Pt, Platinum
 [Xe]6s2
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26. Electron configuration of
ions
 When writing the electron configuration of ions you
follow the same rules, except make sure you use the
CORRECT number of electrons.
 For example C+2 will have two less electrons than
normal.
Instead of the normal C = 1s2 2s2 2p2
 C+2 = 1s2 2s2
 For example C-2 will have two more electrons than
normal.
 C-2= 1s2 2s2 2p4
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27. Orbital Diagrams:
Mapping the electrons
 Orbital diagrams show where an
electron is located.
 Also show electrons are spinning.
 Remember electrons are lazy and
anti-social!
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ENERGY
INCREASES

28. Creating an
Orbital Diagram
 Three rules should be followed when creating orbital diagrams.
 1. The Aufbau Principle states each electron occupies the lowest
energy orbital.
 2. The Pauli Exclusion Principle says that only two electrons can fit
into a single orbital (and they do so facing opposite directions).
 3. Hund’s rule states that electrons go into different orbitals in the
same sub-level before doubling up inside orbitals.
 Example:
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29. Creating an
Orbital Diagram
 Create an orbital diagram for the following elements.
*Remember to check their atomic number for the correct number of electrons you need to map.
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30. Orbital Diagram
Answers
 Your diagrams should look like this . . . . .
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