InterChemArchives_files/Chapter 10

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Transcript InterChemArchives_files/Chapter 10

Chapter 7
• Development of a New Atomic Model
• The Quantum Model of the Atom
• Electron Configuration
• Periodicity
I. Development of a New Atomic Model
A. Light behaves as both a wave and a particle
B. The wave attributes of light include:
1) wavelength - l (lamda)
- the distance from wave to wave (nm)
l
2) frequency - u (nu)
- number of waves per second (s-1; Hz)
watch the
units!!!
3) l
u=c
* c = 3.00 x 108 m/sec
C. Electromagnetic Spectrum
1) this is the range of all wavelengths/frequencies
and what they are called
2) the smaller the wavelength, the more energy it has
Worksheet Problems: # 1,2
D. The particle nature of light - photoelectric effect
1) electromagnetic radiation is emitted in specific
‘packages’ of energy, called photons
2) this radiation does not get to be emitted until the
electrons have obtained a predetermined amount
of minimum energy, called a quantum.
* analogy: a quarter-only coin operated vending machine
Electromagnetic Spectrum
3) The energy associated with a specific wavelength or
frequency is:
E = hc
l
E = hu
h = 6.636 x 10-34 Js
c = 3.00 x 108 m/s
* wavelength must be in METERS…. frequency in Hz
* units for Energy are Joules
Worksheet Problem - # 3
E. Hydrogen atom line emission spectrum
1) ground state - the lowest energy state of an e2) excited state - higher energy state than ground
state
3) the electron in hydrogen are able to be
promoted to higher energy levels when given
a current
4) the color of light given off is made up
wavelengths of energy from the electron giving
off the energy it absorbed
5) the energy released = E2 - E1
6) the resulting spectrum is called a LINE
EMISSION SPECTRUM
7) The Energy released can be calculated once
the wavelength of the emitted photon is known:
Emission Spectrum
II. Quantum Numbers
A. Any mathematical expression with X and Y
variables can be graphed to show the relationships
between them.
B. An expression with X,Y and Z variables will result
in a 3-D graph…..
C. A mathematical equation was used to indicate the
probable location of each electron in an atom
1) the variables are called QUANTUM NUMBERS
2) each quantum number is restricted to allow
only certain values
3) the mathematical results are numerical
answers, but can also be shown graphically
(3-D)
D. These are the 4 quantum numbers, meaning and
allowed values:
symbol
stands for...
n
energy level
shape of
3-D region
l
m
s
orientation of
shape
spin of e-
allowed values
comments
n = 1,2,3...
no zero; no these letters are
l = 0,1,2,3… (n-1)
assigned to each
s,p,d,f
value...
m = - l… 0… + l
s = + 1/2, - 1/2
ex: if n = 1, what l,m and s are allowed?
l = 0 (only)
m = 0 (only)… or ‘s’ shape
s = +1/2 OR - 1/2
ex: if l = 1, then
m = -1, 0, +1
e- spin is either
clockwise or counter
clockwise
C. So, this is the limit of e- each region can have:
s = 2e-…. p = 6e-… d = 10e- … f = 14eD. The first 3 energy levels are limited in having only some
of the shapes:
n = 1….. l = 0 (s shape)
n = 2….. l = 0 (s shape)
l = 1 (p shape)
n = 3….. l = 0 (s shape)
l = 1 ( p shape)
l = 2 (d shape)
E. The energy levels fill up in numerical order to start (I.e.
all the 1st level, all the 2nd level)…..
ex: 1s2 2s2 2p6
Example 1: Write the electron configuration for these
elements:
energy level
# e-
1
H = 1s
He = 1s
shape
2
Li = 1s2 2s1
B = 1s2 2s2 2p1
C = 1s2 2s2 2p2
F… but then the order depends on energy hierarchies
(I.e. its easier to fill some of the 4th before finishing the
3rd)
G. How can you determine the order to follow?
1s
2s
2p
3s
3p
3d
4s
4p
4d
4f
5s
5p
5d
5f
6s
6p
6d
6f
7s
7p
7d
7f
This chart is used by
following the boxes
diagonally from r-l.
ex: Write the electron configuration for Calcium
Ca = 1s2 2s2 2p6 3s2 3p6 4s2
H. Miscellaneous topics
1) noble gas shortcut - write the previous noble
gas (group 18) symbol in square brackets, then
continue from there.
ex: Ca = [Ar] 4s2
2) arrow notation - each orientation is
represented by a line…. each electron by an arrow…
ex: 1s2 2s2 2p6 =
1s
2s
2p
3) Hunds Rule - orbitals of equal energy [degenerate
orbitals] are filled up equally before a 2nd electron is
added.
ex: 1s2 2s2 2p4
1s
2s
2p
a) More number of electrons with same spin
increases stability
b) as electrons are allowed to occupy separate
orbitals, repulsion is minimized
4) Pauli exclusion Principle - two electrons cannot
have the same set of 4 quantum numbers
5) Exceptions to electron configuration order
a) Cr - [Ar] 4s1 3d5
[note 1/2 filled s and d orbitals]
b) Cu - [Ar] 4s1 3d10 [note 1/2 filled s and filled d]
c) Ag - [Kr] 5s1 4d10 [note 1/2 filled s and filled d]
6) Electron configuration of IONS ….
a) BE SURE to remove OUTERMOST electrons
[valence shell electrons]
ex: Zn = 1s2 2s2 2p6 3s2 3p6 4s2 3d10
x 1s2 2s2 2p6 3s2 3p6 4s2 3d8
Zn+2 =
WRONG!
Zn = 1s2 2s2 2p6 3s2 3p6 3d10 4s2 [numerical order]
Zn+2 = 1s2 2s2 2p6 3s2 3p6 3d10
II. Electron Configuration and the Periodic Table
A. Specific regions of the periodic table have
similar outer shell electron configuration
ex: What is the outer shell electron configuration
for Ba?
ex: What is the outer shell electron configuration
for lead?
ex: What is the outer shell electron configuration
for silver? (think before you answer)