Electron Configuration Notes The electron configuration of an atom is the representation of the arrangement of electrons that are distributed among the orbital shells and subshells. Want that in English? It is where you are most likely to find electrons around the nucleus of an atom. The key word is most likely. For example, you are most likely to find humans in cities. So you if zoom in on a map of the US, you are more likely to find a human in a city than in a rural area or wilderness. These configurations are shown by: • The principal quantum number: A number that indicates the energy level • A letter that indicates the type of orbital; s, p, d, f. • A superscript number that indicates the number of electrons in the orbital. 1 S 2 How do you write electron configurations: 1. Determine the total number of electrons to be represented. (For neutral atoms, this will be the atomic number.) 2. Use the Aufbau process to fill the orbitals with electrons. 3. The superscripts will equal the total number of electrons. Example: 12 Mg ls 2 2s 2 2p 6 3s 2
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Electron Configuration NotesThe electron configuration of an atom is the representation of the arrangement of electrons that are distributed among the orbital shells and subshells. Want that in English? It is where you are most likely to find electrons around the nucleus of an atom. The key word is most likely. For example, you are most likely to find humans incities. So you if zoom in on a map of the US, you are more likely to find a human in a city than in a rural area or wilderness.
These configurations are shown by:• The principal quantum number: A number that indicates the energy level • A letter that indicates the type of orbital; s, p, d, f.• A superscript number that indicates the number of electrons in the orbital.
1 S 2
How do you write electron configurations:1. Determine the total number of electrons to be represented. (For neutral atoms, this will be the atomic number.)2. Use the Aufbau process to fill the orbitals with electrons. 3. The superscripts will equal the total number of electrons.Example: 12 Mg ls2 2s2 2p6 3s2
The different energy levels have orbitals.
4 types of orbitals: S P D & F
Three Rules for How Electrons Fill the Orbitals
1. Aufbau
2. Hund’s Rule
3. Pauli Exclusion Principle
Aufbau :Electrons enter orbitals of lowest energy first.
Students must sit in the seat closest to
the door first.
Aufbau
Dang, I have to sit behind the
bus driver.
A. General Rules
• Aufbau Principle– Electrons fill the
lowest energy orbitals first.
– “Lazy Tenant Rule”
Aufbau
Hund’s RuleWhen electrons occupy orbitals of equal energy, one electron enters each orbital until all the orbitals contain one electron spinning the same way.
Only one student per seat until each row is
filled. “Keep your “hunds” to yourself.”
RIGHTWRONG
A. General Rules• Hund’s Rule
– Within a sublevel, place one e- per orbital before pairing them.
– “Empty Bus Seat Rule”
Aufbau
Pauli Exclusion Principle:An atomic orbital may describe at most two electrons.
Only two students per seat allowed!
Pauli says you can’t
sit with us.
A. General Rules• Pauli Exclusion Principle
– Each orbital can hold TWO electrons with opposite spins.
1
2
2 1
2 2
2 2 1
2 2 2
2 2 3
1 1 2 1 3 1 2 4 1 2 5 1 2 2 6 1 2 2 7 1 2 2
Z H sZ He sZ Li s sZ Be s sZ B s s pZ C s s pZ N s s pZ
=======
2 2 4
2 2 5
2 2 6
8 1 2 2 9 1 2 2 10 1 2 2
O s s pZ F s s pZ Ne s s p
===
1s 2s 2p ↓ ↑↓ ↑↑ ↓ ↑↓ ↑↓
↑↓ ↑↑↓ ↓ ↑↓ ↑↓
↓ ↑↑↓ ↑ ↓ ↑↓ ↑↓
↑↓↑↓ ↑↓ ↑↓ ↑↓
↑↓ ↑↓ ↑↓ ↑↓ ↑↓
↑↓ ↑↓ ↑↓ ↑↓ ↑↓
↑↓ ↑↓ ↑↓ ↑↓ ↑↓
↑↓ ↑↓ ↑↓ ↑↓ ↑↓
↑↓ ↑↓ ↑↓ ↑↓ ↑↓
↑↓ ↑↓ ↑↓ ↑↓ ↑↓
Aufbau
Hund’s Rule
Ne
Ar
Kr
Xe
Rn
Ne 1s2 2s2 2p6
Ar 1s2 2s2 2p6 3s2 3p6
Full configuration for Al 1s2 2s2 2p6 3s2 3p1
Shorthand for Al = [Ne] 3s2 3p1
Al
Ne
Ar
Kr
Xe
Rn
10 - Ne 1s2 2s2 2p6
18- Ar 1s2 2s2 2p6 3s2 3p6
Full configuration for Al 1s2 2s2 2p6 3s2 3p1
Shorthand for Al = [Ne] 3s2 3p1
36 - Ar 1s2 2s2 2p6 3s2 3p64s24p63d10
54
86
• The maximum number of electron in each orbital is 2
• The maximum number of ē in each sublevel
sublevel No. of orbital Max no. of ē
s 1 2p 3 6d 5 10f 7 14
• The maximum number of ē in each energy level
level sublevel No. of orbital Max no. of ē
1 s 1 22 s
p13
26
3 spd
135
26
10
8
18
Electron Configuration LabPage 371
Copy TitlePurpose, Data Table, Analysis Questions
---------------1. Add a few drops of each
compound to the reaction surface. Record color.
2. Add 3 drops of NaOH to each and record observations.
NaCl MgSO4 AlCl3
FeCl3 CaCl2 NiSO4
CuSO4 ZnCl2 AgNO3
A mnemonic diagram for the building-up order (diagonal rule).
You may have to memorize this in college, but in my class you will always have an Aufbau diagram to use.
Electron Configuration of Sodium
IV. Electron ConfigurationElectrons in Atoms
O8e-
• Orbital Diagram
Electron Configuration
1s2 2s2 2p4
B. Notation
1s 2s 2p
Shorthand Configuration
S 16e-
Valence ElectronsCore Electrons
S 16e- [Ne] 3s2 3p4
1s2 2s2 2p6 3s2 3p4
B. Notation• Longhand Configuration
© 1998 by Harcourt Brace & Company
sp
d (n-1)
f (n-2)
1234567
67
C. Periodic Patterns
Electron Configurations of Ions
Remember-elements like to have an octet of 8 valence electrons.
• Elements with 1 – 3 valenceelectrons tend to “lose” them
• Elements with 5 – 7 valence electrons gain electrons to form an octet.
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