Transcript CH5 Electrons

Ch. 5 Electrons
Describe Atomic Models
Identify energy positions of electrons
Use quantum mechanical model
To write electron configurations
Development of Atomic Models
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Rutherford’s Model
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Orbital Model: Electrons
orbiting the nucleus like
planets around the sun
Explained size and
charge of nucleus
COULD NOT explain
chemical properties of
elements!
We needed a better
model….
Neils Bohr and his Model
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Student of Rutherford
Believed the model at the time needed improvement
Bohr accounted for new discoveries in how the
energy of an atom changed when absorbing or
emitting light
Bohr Model
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Proposed that an electron is found ONLY in
specific circular paths, or orbits, around the
nucleus.
Each “orbit” has a fixed energy or Energy Level.
Electrons can move from one level to another.
They must release energy when moving down
and gain energy when moving up a level.
Bohr Model showing 1st and 2nd
Energy level
Energy Levels
Increasing energy
Fifth
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Fourth
Third
Second
First
Nucleus
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Further away
from the nucleus
means more
energy.
There is no “in
between” energy
levels
Quantum Energy
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Amount of energy
required to move an
electron from one
energy level to
another.
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E=hv
H= Planks constant
(6.626X10-34js)
V= frequency
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Energy levels
The energy levels are not equally spaced.
 Higher levels are closer together
 Less NRG to climb “rungs at top of ladder”
 Light given off by burned or electrically excited
element corresponds to the energy the electron
absorbs when “excited”. This energy is then
release when the electron returns to it’s resting
“ground” state.
Electron Energy level simulation
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Maximum number of electrons in each
energy level
Level
1
2
3
4
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Number Electrons
2
8
18
32
This explained why some elements formed ions with a
different number of electrons compared to the neutral
atom.
Some elements gain electrons to become more
negative
Some elements loose electrons and become positive
Sodium ion looses 1 e- making it
positive
Rutherford & Bohr Models
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Based on describing e- paths
But as new research came along so did the time
for new models.
Quantum Mechanical Model accounted for the
“Wave” nature of light
The figure illustrates that
electrons orbit the nucleus
only in whole-number
wavelengths.
Quantum Mechanic Model
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Proposed by Erwin Schrödinger (Austrian)
1926
Used mathematical equations to describe
electrons in atoms based on the probability
of their location
Developed Quantum Mechanical Model
Atomic Theory Song Chemistry - YouTube
Quantum Mech. Model
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Like Bohr, his model
of the atom restricted
the NRG of e-’s to
certain values.
Unlike Bohr, this
model does not say
where the electrons
are exactly “orbiting”
Quantum Mechanical Model
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Has energy levels for electrons. Ex. 1,2,3,4
Each energy level is divided into a number
sublevels.
Energy level 1 has 1 sublevel, 2 has 2, level 3
has 3 sublevels.
Each sublevel is made of a type of orbital of
particular shape.
Orbitals are labeled as either type s,p,d,or f
The Electron Hotel
Shapes of Electron Orbital
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Energy levels are labeled, like floors in a
hotel.
Sub-Levels s,p,d,f are like the rooms
Orbital: region of space in which there is a
high probability of finding an e- (beds in
the Hotel)
“Hotel Floors” called Principal Quantum #’s
The location of an electron can be
described using these “quantum numbers”
Example 1s22s22p3
S orbitals
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There is one s orbital for every energy level
Spherical shaped
Each s orbital can hold 2 electrons
Called the 1s, 2s, 3s, etc.. orbitals.
P orbitals
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Start at the second energy level
3 different directions
3 different shapes
Each can hold 2 electrons
D orbitals
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Start at the second energy level
4 different “clover” shapes, 1is not clover
Each can hold 2 electrons
F orbitals
Summary
# of
Max
orbitals electrons
Starts at
energy level
s
1
2
1
p
3
6
2
d
5
10
3
f
7
14
4
Links
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filing order applet
electron configuration tables
practice quiz
periodic table