Transcript Electronic Configuration

Chapter 8
Electron Configuration,
Periodicity, and
Properties of the Elements
Dr. S. M. Condren
Electromagnetic Radiation
Electromagnetic wave
• A wave of energy having a frequency within
the electromagnetic spectrum and
propagated as a periodic disturbance of the
electromagnetic field when an electric
charge oscillates or accelerates.
Dr. S. M. Condren
Dr. S. M. Condren
Electromagnetic Radiation
Electromagnetic wave
• wavelength
• frequency
• amplitude
Dr. S. M. Condren
Dr. S. M. Condren
Quantum Mechanics
Quantum theory
• the theory of the structure and behavior of
atoms and molecules.
Dr. S. M. Condren
Black Body Radiation
http://www.cbu.edu/~mcondren/C11599/BBvis.mov
Dr. S. M. Condren
Electromagnetic Radiation
nl= c
where
n => frequency
l => wavelength
c => speed of light
Dr. S. M. Condren
Electromagnetic Radiation
Ehi - Elo = hc/l
where E => energy
h => Planck's constant
c => speed of light
l => wavelength
Dr. S. M. Condren
Photoelectric Effect
• the emission of electrons by substances,
especially metals, when light falls on their
surfaces.
Dr. S. M. Condren
Dr. S. M. Condren
Photons
The quantum of electromagnetic energy,
generally regarded as a discrete particle
having zero mass, no electric charge, and an
indefinitely long lifetime.
Dr. S. M. Condren
Dr. S. M. Condren
Line Spectrum
A spectrum produced by a luminous gas or
vapor and appearing as distinct lines
characteristic of the various elements
constituting the gas.
Dr. S. M. Condren
Emission Spectrum
The spectrum of bright lines, bands, or
continuous radiation characteristic of and
determined by a specific emitting substance
subjected to a specific kind of excitation.
Dr. S. M. Condren
Ground State
The state of least possible energy in a physical
system, as of elementary particles. Also
called ground level.
Dr. S. M. Condren
Excited State
Being at an energy level higher than the
ground state.
Dr. S. M. Condren
Dr. S. M. Condren
Absorption Spectrum
• Light shinning on a
sample causes
electrons to be excited
from the ground state
to an excited state
• wavelengths of that
energy are removed
from transmitted
spectra
Dr. S. M. Condren
Knowing diamond is transparent, which
curve best represents the absorption
spectrum of diamond (see below)?
A, B, C
Dr. S. M. Condren
The Atomic Spectrum of Hydrogen
and the Bohr Model
Bohr Model for the Hydrogen Atom
mnr = nh/2p
Dr. S. M. Condren
Bohr Model
Netscape
• NCSU Materials Science site
– Chapter 2 Atomic Bonding
• I Atoms and Electrons
– slide 2
or
• http://odin.cbu.edu/~mcondren/bohr.html
or through the CHEM 115 homepage
Dr. S. M. Condren
Bohr Atom
Dr. S. M. Condren
Bohr Model
E = -B/n2
where n => quantum number
1, 2, 3, 4, 5, 6, 7, etc
Dr. S. M. Condren
Bohr Model
E = (-2.179 X 10-18 J/part.)
(6.022 X 1023 part./mole)
(1 kJ/103 J)/n2
= (-1312 kJ/mol)(1/n2)
Dr. S. M. Condren
Bohr Model
for hydrogen
ground state: n = 1
excited state: n > 1
Dr. S. M. Condren
Dr. S. M. Condren
Line Spectra
Lyman series => ultraviolet
n > 1 ==> n = 1
Balmer series => visible light
n > 2 ==> n = 2
Paschen series => infrared
n > 3 ==> n = 3
Dr. S. M. Condren
Line Spectra
See CHEMWORKS software
Dr. S. M. Condren
According to the energy diagram below for
the Bohr model of the hydrogen atom, if an
electron jumps from E1 to E2, energy is
absorbed
emitted
not involved
Dr. S. M. Condren
Heisenberg, Werner
1901–76, German physicist
1932 Nobel Prize in physics
A founder of QUANTUM MECHANICS, he
is famous for his uncertainty principle,
which states that it is impossible to
determine both the position and momentum
of a subatomic particle (such as the
electron) with arbitrarily high accuracy.
Dr. S. M. Condren
Heissenberg Uncertainty Principle
“it is impossible to determine both the position
and momentum of a subatomic particle
(such as the electron) with arbitrarily high
accuracy”
The effect of this principle is to convert the
laws of physics into statements about
relative, instead of absolute, certainties.
Dr. S. M. Condren
Orbitals
• region of probability of finding an electron
around the nucleus
• 4 types => s p d f
• maximum of 2 electrons per orbital
Dr. S. M. Condren
Pure Atomic Orbitals
s
p
d
f
shape
# of orbitals / energy level
spherical
1
dumbbell
3
complex
5
very complex
7
Dr. S. M. Condren
Dr. S. M. Condren
Shapes of Orbitals
http://www.colby.edu/chemistry/OChem/DEMOS/Orbitals.html
Dr. S. M. Condren
Dr. S. M. Condren
Dr. S. M. Condren
Dr. S. M. Condren
Dr. S. M. Condren
Electronic Configurations
• The shorthand representation of the
occupancy of the energy levels (shells and
subshells) of an atom by electrons.
Dr. S. M. Condren
Electronic Configuration
shells
subshells
=>
=>
energy levels
orbitals
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Electron Filling Order
Diagram
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
3d
4d 4f
5d 5f
6d
Dr. S. M. Condren
Electronic Configuration
H atom
1 electron
1s1
Dr. S. M. Condren
Electronic Configuration
He atom
2 electrons
1s2
Dr. S. M. Condren
Electronic Configuration
Li atom
3 electrons
1s2, 2s1
Dr. S. M. Condren
Electronic Configuration
Cl atom
17 electrons
1s2, 2s2, 2p6, 3s2, 3p5
Dr. S. M. Condren
Electronic Configuration
As atom
33 electons
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p3
or
[Ar] 4s2, 3d10, 4p3
Dr. S. M. Condren
Mn: [Ar]4s2 3d?
How many d electrons does Mn have?
4, 5, 6
Dr. S. M. Condren
Electronic Configuration
negative ions
add electron(s), 1 electron for each negative
charge
Dr. S. M. Condren
Electronic Configuration
S-2 ion
(16 + 2)electrons
1s2, 2s2, 2p6, 3s2, 3p6
Dr. S. M. Condren
Electronic Configuration
positive ions
remove electron(s), 1 electron for each
positive charge
Dr. S. M. Condren
Electronic Configuration
Mg+2 ion
(12-2)electrons
1s2, 2s2, 2p6
Dr. S. M. Condren
How many valence electrons are in Cl,
[Ne]3s2 3p5?
2, 5, 7
Dr. S. M. Condren
For Cl to achieve a noble gas configuration,
it is more likely that
electrons would be added
electrons would be removed
Dr. S. M. Condren
Magnetism
• Result of the spin of electrons
• diamagnetism - no unpaired electrons
• paramagnetism - one or more unpaired
electrons
• ferromagentism - case of paramagnetism
where the substance retains its magnetism
Dr. S. M. Condren
paramagnetic
ferromagnetic
Dr. S. M. Condren
Trends in the
Periodic Table
•
•
•
•
atomic radius
ionic radius
ionization energy
electron affinity
Dr. S. M. Condren
Atomic Radius
• decrease left to right across a period
– as nuclear charge increases, number of
electrons increase; however, the nucleus acts as
a unit charge while the electrons act
independently, pulling electrons towards the
nucleus, decreasing size
Dr. S. M. Condren
Atomic Radius
• increase top to bottom down a group
– each additional electron “shell” shields the
outer electrons from the nuclear charge
Zeff = Z - S
where Zeff => effective nuclear charge
Z => nuclear charge, atomic number
S => shielding constant
Dr. S. M. Condren
Atomic Radius
• increases from upper right corner to the
lower left corner
Dr. S. M. Condren
Dr. S. M. Condren
Dr. S. M. Condren
Ionic Radius
• same trends as for atomic radius
• positive ions smaller than atom
• negative ions larger than atom
Dr. S. M. Condren
Ionic Radius
Isoelectronic Series
• series of negative ions, noble gas atom, and
positive ions with the same electronic
confiuration
• size decreases as “positive charge” of the
nucleus increases
Dr. S. M. Condren
Dr. S. M. Condren
Dr. S. M. Condren
Ge is a semiconductor. If half of the Ge
atoms of a sample of Ge are replaced with
Ga atoms, with what element should the
other half of the Ga atoms be replaced in
order for this new compound to be
isoelectronic with Ge?
Sn, As, Se
Dr. S. M. Condren
Ionization Energy
• energy necessary to remove an electron to
form a positive ion
• low value for metals, electrons easily
removed
• high value for non-metals, electrons
difficult to remove
• increases from lower left corner of periodic
table to the upper right corner
Dr. S. M. Condren
Ionization Energies
first ionization energy
• energy to remove first electron from an
atom
second ionization energy
• energy to remove second electron from a +1
ion
etc.
Dr. S. M. Condren
Dr. S. M. Condren
Electron Affinity
• energy released when an electron is added
to an atom
• same trends as ionization energy, increases
from lower left corner to the upper right
corner
• metals have low “EA”
• nonmetals have high “EA”
Dr. S. M. Condren