Download Electron Configuration

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Electron configuration is a shorthand notation
that shows electron arrangement within
orbitals.
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Electron configuration can be written in one of
3 methods:
1. Energy-Level Diagrams (orbital diagram)
2. Complete electron configuration
3. Condensed electron configuration (AKA noble gas
configuration)

Atomic spectra conclude that electrons in an
atom have different energies

Under normal conditions (i.e., ground state),
an energy-level diagram can show the relative
energies of electrons in various orbitals

The number of electrons in an atom is equal to the
atomic number

Each added electron will enter the orbitals in the
order of increasing energy

Orbitals of lowest energy are filled first

An orbital cannot take more than 2 electrons.
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Every orbital in a subshell is singly occupied
with one electron before any one orbital is
doubly occupied

All electrons in singly occupied orbitals have
the same spin.

Analogy: “The Bus Seat Rule” – when
boarding the bus, you would take an empty
seat rather than sit beside someone.

Convey the same information, but in a more
condensed form

In a single line, all orbitals and electrons are listed in
order of increasing energy level

There is, of course, a trend seen in the periodic table for
electron configuration
 The n-value for s and p orbitals correspond to the row numbers on the
periodic table
 The l-values correspond to the columns
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s block: Groups 1 & 2
p block: Groups 13-18
d block: Transition elements
f block: inner transition elements
Lanthanides (elements #57-70)
Actinides (elements #89-102)

To find the electron configuration of a given element, simply
locate its position on the periodic table

Determine the electron configuration of gallium

As electron configurations can also be long and
tedious, there is a shorthand form that conveys the
same information

This involves looking at the most recent noble gas
(since they are stable and all orbitals are full) and then
continuing the electron configuration from there

Cl: 1s2 2s2 2p6 3s2 3p5
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Sn: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p2
→Sn: [Kr] 5s2 4d10 5p2
→
Cl: [Ne] 3s2 3p5
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Anions
 Simple! Simply add the correct number of “extra”
electrons

Try it for Br1-
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Cations
 Subtract electrons from the highest principal
quantum number (n)
 To do so, it’s best to write the configuration for the
neutral atom first

Try it for Ga3+
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Read Pages 185-193
 On Page 191, #1-4
 On Page 194, #6-11