Chapter 5 Lecture
Basic Chemistry
Fourth Edition
Chapter 5 Electronic Structure and
Periodic Trends
5.4 Orbital Diagrams and Electron Configurations
Learning Goal Draw the orbital
diagram and write the electron
configuration for an element.
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Orbital Diagrams
Orbital diagrams
• explain how electrons are arranged within
the atom
• show the order in which electrons are placed
in orbitals
• use boxes to represent orbitals
• use colors to represent sublevels s, p, d, f
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Orbital Diagram
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Electrons in Orbital Diagrams
To place electrons in orbital diagrams, electrons
• are represented by arrows and the direction of
the arrow is used to represent electron spin
• fill orbitals in order of increasing energy
beginning with 1s, then 2s and 2p
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Electrons in Orbital Diagrams
Orbitals can hold a maximum of two electrons.
Within sublevels that contain multiple orbitals,
one electron is placed in each orbital with
parallel spins before the electrons are paired.
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Electron Configurations
Chemists use a notation called the electron
configuration to indicate placement of electrons
in an atom.
The lowest energy sublevel is written first, then
sublevels with increasing energies.
The number of electrons in each sublevel is
written as a superscript.
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Period 1: Hydrogen and Helium
The 1s is written first; it has the lowest energy.
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Period 2: Lithium to Neon
• Period 2 begins with lithium, which has three
electrons, 1s2 2s1.
• After the 2s is filled, the 2p orbitals are filled.
• One electron is placed in each p orbital before
they are paired.
• An abbreviated configuration uses a noble gas
in brackets to represent the filled electron
configuration of that noble gas.
[He] 2s1
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Period 2: Lithium to Neon
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Period 2: Lithium to Neon
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Guide to Drawing Orbital Diagrams
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Sample Problem
Draw the orbital diagram for nitrogen.
Step 1 Draw boxes to represent the occupied
orbitals. Nitrogen has an atomic number
of seven, which means it has seven
electrons. Draw boxes to represent the
1s, 2s, and 2p orbitals.
1s
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2s
2p
Sample Problem
Draw the orbital diagram for nitrogen.
Step 2 Place a pair of electrons in the last
occupied sublevel in separate orbitals.
We place the remaining three electrons
in the 2s orbitals.
1s
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2s
2p
Sample Problem
Draw the orbital diagram for nitrogen.
Step 3 Place remaining electrons with
opposite spins in each filled orbital.
First we place a pair of electrons with
opposite spins in the 2p orbitals, with
arrows in the same direction.
1s
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2s
2p
Period 3: Sodium to Argon
[Ne] is used to represent 1s2 2s2 2p6.
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Period 3: Sodium to Argon
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Learning Check
Draw the abbreviated orbital diagram for
aluminum, [Ne] 3s2 3p1.
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Solution
Draw the abbreviated orbital diagram for
aluminum, [Ne] 3s2 3p1.
1. The preceding noble gas is Ne; we use this
to represent 1s2 2s2 2p6.
2. Fill the 3s, and add the last electron to the
3p sublevel.
3s
[Ne]
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3p