Chapter 5:
Electrons in Atoms
Electron Arrangement in
Atoms
Learning Target
You will determine the electron
configuration and orbital notation for atoms
and ions.
Electron Configuration
The atomic number
tells us the number of
electrons in an atom.
The electrons fill each
energy level, sublevel
and orbital like an ice
tray. Once a sublevel
is filled, the next energy
level and sublevel are
filled and so on.
Principal
Energy
Level
Number of
sublevels
Type of sublevel
Maximum
number of
electrons
n=1
1
1s (1 orbital)
2
n=2
2
2s (1 orbital),
2p (3 orbitals)
8
n=3
3
3s (1 orbital),
3p (3 orbitals),
3d (5 orbitals)
18
n=4
4
4s (1 orbital),
4p (3 orbitals),
4d (5 orbitals),
4f (7 orbitals)
32
You will determine the electron configuration and orbital notation for atoms and ions.
Draw this on the back of your periodic table
You will determine the electron configuration and orbital notation for atoms and ions.
s sublevel
note on periodic table
You will determine the electron configuration and orbital notation for atoms and ions.
p sublevel
note on periodic table
You will determine the electron configuration and orbital notation for atoms and ions.
d sublevel
note on periodic table
You will determine the electron configuration and orbital notation for atoms and ions.
f sublevel
note on periodic table
You will determine the electron configuration and orbital notation for atoms and ions.
Energy Levels
note on periodic table
You will determine the electron configuration and orbital notation for atoms and ions.
Energy Levels and Orbitals
You will determine the electron configuration and orbital notation for atoms and ions.
Electron Configuration
Let’s write electron
configurations for the
following atoms:
1. hydrogen
2. nitrogen
3. aluminum
Answers:
1. hydrogen – 1s1
2. nitrogen – 1s22s22p3
3. Aluminum 1s22s22p63s23p1
You will determine the electron configuration and orbital notation for atoms and ions.
Electron Configuration
Let’s write electron
configurations for the
following atoms
(cont.):
1. helium
2. oxygen
3. silicon
Answers:
1. helium - 1s2
2. oxygen - 1s22s22p4
3. silicon 1s22s22p63s23p2
You will determine the electron configuration and orbital notation for atoms and ions.
Try some on your own
Write the electron configuration for the
following atoms:
sodium
phosphorus
potassium
You will determine the electron configuration and orbital notation for atoms and ions.
Answers
Write the electron configuration for the
following atoms:
sodium – 1s22s22p63s1
phosphorus - 1s22s22p63s23p3
potassium - 1s22s22p63s23p64s1
You will determine the electron configuration and orbital notation for atoms and ions.
Orbital Notation
Orbital notation is a way
of drawing electron
configurations.
A box or blank indicates
the space for an orbital.
Remember an orbital
can hold two electrons.
An orbital will
correspond to each
energy level and
sublevel in the
configuration
s
#
Max #
Orbitals
e1
2
p
3
6
d
5
10
f
7
14
You will determine the electron configuration and orbital notation for atoms and ions.
Orbital Notation
The last property of orbitals to talk about is
electron spin.
Spin is represented with an arrow: ↑ or ↓
Two electrons must have opposite spins to
occupy the same orbital (Pauli exclusion
principle)
You will determine the electron configuration and orbital notation for atoms and ions.
Examples of orbital notations
You will determine the electron configuration and orbital notation for atoms and ions.
Orbital Notation
Look at these examples of orbital
notations. Let’s go through how they got
these:
hydrogen
nitrogen
helium
You will determine the electron configuration and orbital notation for atoms and ions.
Try some on your own
Write the orbital notation for the following
atoms:
sulfur
silicon
magnesium
You will determine the electron configuration and orbital notation for atoms and ions.
Electron Configuration
Electron Configuration and Orbital
Notation change for elements after the first
20.
This is because instead of going in order
of each energy level and sublevel, we
jump from the 4s to 3d
An example of an electron configuration
with this: Se - 1s22s22p63s23p64s23d104p4
Notice the jump from 4s to 3d then back to 4p
You will determine the electron configuration and orbital notation for atoms and ions.
Electron Configuration
Let’s try some examples together. Give
the electron configuration for gallium (Ga),
bromine (Br) and hafnium (Hf).
Ga – 1s22s22p63s23p64s23d104p1
Br - 1s22s22p63s23p64s23d104p5
Hf 1s22s22p63s23p64s23d104p65s24d105p66s24f145d2
You will determine the electron configuration and orbital notation for atoms and ions.
Try these on your own
Give the electron configurations for the
following elements:
– tin (Sn)
– lead (Pb)
– polonium (Po)
– iodine (I)
You will determine the electron configuration and orbital notation for atoms and ions.
Answers
Give the electron configurations for the following
elements:
tin (Sn) - 1s22s22p63s23p64s23d104p65s24d105p2
lead (Pb) 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p2
pollonium (Po) –
1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p4
iodine (I) - 1s22s22p63s23p64s23d104p65s24d105p5
You will determine the electron configuration and orbital notation for atoms and ions.
Orbital Notations
Give the orbital notations for the following
elements:
tin (Sn)
lead (Pb)
pollonium (Po)
iodine (I)
You will determine the electron configuration and orbital notation for atoms and ions.
Noble Gas Shortcut
Notice the noble gases fill energy levels
entirely, filling all the valence electrons.
– This is why there is little to no reactivity with
other atoms.
Since the energy level is filled entirely we
can use a noble gas shortcut when writing
electron configurations.
You will determine the electron configuration and orbital notation for atoms and ions.
Noble Gas Shortcut
An example of this (Gallium):
full: 1s22s22p63s23p64s23d104p1
noble gas short cut: [Ar] 4s23d104p1
The noble gas that precedes the element
is the noble gas used in the shortcut.
Its electron configuration is replaced with
the noble gas in brackets.
Then the remaining electron configuration
is written after.
You will determine the electron configuration and orbital notation for atoms and ions.
Examples:
Write the electron configuration using the
noble gas shortcut for bromine (Br), tin
(Sn), Pollonium (Po), and fluorine (F).
Br: [Ar]4s23d104p5
Sn: [Kr]5s24d105p2
Po: [Xe]6s24f145d106p4
F: [He]2s22p5
You will determine the electron configuration and orbital notation for atoms and ions.
Try on your own
Write the electron configuration using the
noble gas shortcut for silicon (Si), lead
(Pb), Iodine (I) and cesium (Cs).
Si: [Ne]3s23p2
Pb: [Xe]6s24f145d106p2
I: [Kr]5s24d105p5
Cs: [Xe]6s1
You will determine the electron configuration and orbital notation for atoms and ions.
Isoelectronic Ions
Ions can have same electronic
configurations as other elements and ions.
When this happens ions and/or elements
are "isoelectronic" with one another.
http://www.iun.edu/~cpanhd/C101webnote
s/chemical-bond/isoelectronic.html
You will determine the electron configuration and orbital notation for atoms and ions.
Practice/Try on your own
1. Write the electron
configuration for the
magnesium ion.
2. Write the electron
configuration for the
phosphorus ion.
Write the electron
configuration for
neon. Name one
positive ion and one
negative ion with the
same configuration.
You will determine the electron configuration and orbital notation for atoms and ions.