Warm-up February 12th
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What is the wavelength of light and
portion of the EMS is it on when an
electron falls from the:
a. 4th to the 2nd energy level?
b. 6th-3rd?
c. 3rd to 2nd?
RULES GOVERNING eCONFIGURATIONS
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Aufbau principle- an e- occupies the lowestenergy orbital first
Pauli exclusion principle- each orbital can hold
TWO electrons with opposite spins
Hund’s Rule- within a sublevel, place one eper orbital before pairing them
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Empty bus seat rule!
ELECTRON CONFIGURATIONS
-arrangement of electrons in an atom
Sublevel
s
p
d
f
orbitals
1
3
5
7
total e2
6
10
14
Energy level
Sublevels
Total orbitals
Total number
electrons it can
hold
1
s
1
2
2
s,p
4
8
3
s,p,d
9
18
4
s,p,d,f
16
32
5
s,p,d,f
16
32
6
s,p,d,f
16
32
7
s,p,d,f
16
32
Two types of notation for
electrons
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Electron Configuration Notation
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number of electrons in sublevel is added as
a superscript
1s22s22p63s23p64s1
Orbital Notation:
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an orbital is written as a line
each orbital has a name written below it
electrons are drawn as arrows (up and
down)
Electron configuration pattern
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
Electron configuration pattern
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
Electron configurations
Follow the pattern in the previous slide
and fill maximum number of electrons for
each sublevel until you get the number of
electrons you should have for the specific
atom
 Example: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
This is an e- configuration for bromine
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Warm-up February 16th
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Write the electron configurations for the
following elements
Aluminum (Al)
Chromium (Cr)
Yttrium (Y)
Orbital diagrams
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Follow same pattern for e- configurations,
but you represent orbitals with lines and
electrons with up and down arrows
Silicon
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1s
number of electrons: 14
last electron is in sublevel: 3p
2s
2p
3s
3p
Valence Electrons- the electrons in the outermost
energy level
Chlorine
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number of electrons: 17
last electron is in sublevel: 3p
1s
2s
2p
3s
3p
Sodium
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1s
number of electrons: 11
last electron is in sublevel: 3s
2s
1s2 2s2 2p6 3s1
2p
3s
Bromine
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1s
4s
number of electrons: 35
last electron is in sublevel: 4p
2s
2p
3s
3d
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
3p
4p
Argon
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1s
number of electrons: 18
last electron is in sublevel: 3p
2s
2p
1s2 2s2 2p6 3s2 3p6
3s
3p
Noble Gas Notation
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short hand for larger atoms
configuration for the last noble gas is
abbreviated by the noble gas’s symbol in
brackets
Bohr Models
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Bohr models show only what energy level
the electrons are on
Order for Filling Sublevels
Noble gas configurations
(short-cut)
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Write the noble gas in brackets (the one
that comes before the element that you
are writing it for) then go to the row that
your element is in and write the row
number then fill according to the blocks