Life on the EDGE!!!!!
What were some of those models of
the atom again??!!
Rutherford’s Model: The Nuclear Model
He discovered that atoms have a
nucleus with positively charged
protons inside! (The particles he
was shooting at the gold atoms
went right through most of the
time, but 1/8000 times it would
bounce off of the dense, positively
charged nucleus!
Bohr’s Model: The Planetary Model
The atom has protons in
the center (the nucleus)
and electrons are
located at specific
distances from the
nucleus.
Electrons cannot fall into
nucleus because they have a
fixed energy.
Electron Cloud Model
• Location of
electron within
energy level is
based on
probability
Core vs. Valence Electrons
Valence Electrons: The electrons found in the
outermost (valence) shell of an atom.
Core Electrons: All other electrons found in an
atom other than the valence electrons.
How many valence electrons
does aluminum have? 3
How many core electrons does
aluminum have? 10
Principal Energy Levels (AKA: SHELLS!)
Energy Level (AKA Shell): the region around the
nucleus where the electron is likely to be
moving
7
6
5
3
4
2
1
Ladder analogy:
Lowest rung = lowest energy
Can’t stand between rungs
What do these energy levels correlate
to on the periodic table?
Quiz: How many energy levels
(shells) would Magnesium have
electrons in?
Answer: 3 (because it’s in the 3rd
period!)
Shells, subshells and orbitals, OH MY!
Shells contain subshells. Subshells contain orbitals.
There are 4 types of subshells: s, p, d & f
Nuc.
Subshells: s, p, d & f
Subshells are
further
broken into
orbitals.
Each orbital can
hold a
maximum of
2 electrons
Shell
1
2
3
4
Subshells
Present
s
s,p
s,p,d
s,p,d,f
Draw the filled orbitals
for each subshell
Total # of
e- possible
in shell
2
s
8
s
p
18
s
p
d
32
Numbers and kinds of atomic orbitals
depend on the energy level.
Lowest energy level (1) has one sublevel: 1s
“s” orbital is spherical
Electron probability density for Hydrogen
2s Beryllium Orbital probability distribution
2s Boron Orbital probability distribution
2nd principal energy level has 2
sublevels: 2s and 2p
• p sublevel: 3 dumbbell shaped orbitals of
equal energy
2 overlapped p-type orbitals for carbon. The different orbitals are
different colors (one is horizontal and one is vertical).
3rd Energy level has 3 sublevels: 3s, 3p,
3d
• d sublevel has five d orbitals of equal energy
4th Energy level has 4 sublevels: 4s, 4p,
4d, 4f
• f sublevel has seven orbitals of equal energy
• How many total orbitals (sublevels) are there in
the 4th energy level?
Another Trend on the Periodic Table!
What is the maximum number of
electrons that can fit in each subshell?
Shell
Subshells Max # of
Present electrons
1
s
2
2
s,p
8
3
s,p,d
18
4
s,p,d,f
32
FORMULA
for the
Maximum #
of electrons
in shell =
2
2n
Increasing Energy
QUIZ Yourself!
• You identify two different electrons. One is in the 1st
energy level, the other is found in the the 4th energy
level. Which electron has more energy?
Answer: The 4th energy level electron!
Explanation: The further away an
electron is from the nucleus, the
higher the energy it has.
Would an electron in the 4s or 3d
subshell have more energy?
3d!
Electron Configuration
Electron Configuration: a list of all the subshells
that have electrons for a given element.
Calcium: 1s22s22p63s23p64s2
Examples:
Hydrogen:
• 1s1
Carbon:
• 1s22s22p2
Fluorine
• 1s22s22p5
Magnesium
• 1s22s22p63s2
Electron Filling Order
More Practice
Bromine
• 1s22s22p63s23p64s23d104p5
Silver
• 1s22s22p63s23p64s23d104p65s24d9
Noble Gas Shortcut!!
– How does it work?
• Use the preceding noble gas as a “placeholder”
• Example:
Sodium = 1s22s22p63s1
Rather than writing the whole configuration, can
write
Sodium = [Ne]3s1
• Write the symbol of the noble gas in brackets [ ]
• Show ALL the electrons that are beyond the noble
gas, not just the last term
Example: Scandium, Sc:
[Ar] 4s23d1
Practice
• Using the Noble Gas shortcut, write the
electron configuration for:
Barium
• [Xe] 6s2
Selenium
• [Ar] 4s23d104p4
How many Valence electrons in the
following?
1s22s22p63s23p64s23d104p4
6 valence electrons
1s22s22p63s23p64s23d104p4
SELENIUM