Chemistry 481(01) Spring 2015
Instructor: Dr. Upali Siriwardane
e-mail: upali@latech.edu
Office: CTH 311 Phone 257-4941
Office Hours:
M,W 8:00-9:00 & 11:00-12:00 am;
Tu,Th, F 9:30 - 11:30 a.m.
April 7 , 2015: Test 1 (Chapters 1, 2, 3)
April 30, 2015: Test 2 (Chapters 5, 6 & 7)
May 19, 2015: Test 3 (Chapters. 19 & 20)
May 19, Make Up: Comprehensive covering all Chapters
Chemistry 481, Spring 2015, LA Tech
Chapter-1-1
Origin of Elements in the Universe
Scientists have long based the origin of our
Universe on the Big Bang Theory. According to this
theory, our universe was simply an expanding fairly
cold entity consisting of only Hydrogen and Helium
during it's incipient stages. Over the expanse of many
years, and through a continuing process of fusion and
fission, our universe has come to consist of numerous
chemical elements, four terrestrial planets(Earth,
Mars, Venus, and Mercury), and five giant gas
planets(Saturn, Jupiter, Neptune, Pluto, and Uranus).
Chemistry 481, Spring 2015, LA Tech
Chapter-1-2
Predicted Nuclear Fusion of
Light Elements in the Young,
Hot Universe
Chemistry 481, Spring 2015, LA Tech
Chapter-1-3
Few minutes after big Bang
Chemistry 481, Spring 2015, LA Tech
Chapter-1-4
Eight Steps in the History of the Earth
1. The Big Bang
2. Star Formation
3. Supernova Explosion
4. Solar Nebula Condenses
5. Sun & Planetary Rings Form
6. Earth Forms
7. Earth's Core Forms
8. Oceans & Atmosphere Forms
Chemistry 481, Spring 2015, LA Tech
Chapter-1-5
Nuclear
Burning
Chemistry 481, Spring 2015, LA Tech
Chapter-1-6
Origin of the Elements: Nucleosynthesis
•Elements formed in the universe's original stars
were made from hydrogen gas condensing due to
gravity. These young stars "burned" hydrogen in
fusion reactions to produce helium and the
hydrogen was depleted. Reactions such as those
below built up all the heavier elements up to atomic
number 26 in the periodic table.
•When the stars got old they exploded in a super
nova, spreading the new elements into space with
high flux of neutrons to produce heavy elements by
neutron capture.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-7
1. What are the two basic types of nuclear
reactions? Give examples of each that occur during
the formation of the Universe
Chemistry 481, Spring 2015, LA Tech
Chapter-1-8
Cosmic Abundances
Chemistry 481, Spring 2015, LA Tech
Chapter-1-9
Balancing Nuclear Reactions
Two conditions must be met to balance nuclear
reactions:
1. The sum of the masses of the reactants must equal
the sum of the masses of the products. (i.e., the values
of A must balance on both sides of the equation.)
2. The sum of the protons for the reactants must equal
the sum of the protons for the products. (i.e., the values
of Z must balance on both sides of the equation.)
Chemistry 481, Spring 2015, LA Tech
Chapter-1-10
Balancing Nuclear Reactions
2. Complete the following Nuclear reactions:
a) Uranium – 238 decays by alpha radiation to
produce what other element?
b) Uranium – 238 decays by alpha radiation to
produce what other element?
c) What element did we start out with if the result
of beta decay is bismuth– 214?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-11
Balancing Nuclear Reactions
2. Complete the following Nuclear reactions:
d) What element is produced when mercury – 201
captures an inner shell electron with the production
of a gamma ray to release excess energy?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-12
3. Predict the most likely modes of decay and the
products of decay of the following nuclides:
17F:
105Ag:
185Ta:
Chemistry 481, Spring 2015, LA Tech
Chapter-1-13
Bonding Energy Curve
Chemistry 481, Spring 2015, LA Tech
Chapter-1-14
Nuclear Binding Energy
The binding energy of a nucleus is a measure of how
tightly its protons and neutrons are held
together by the nuclear forces. The binding energy
per nucleon, the energy required to remove
one neutron or proton from a nucleus, is a function
of the mass number A. (Dm) –mass defect
(Dm) = Mass of Nuclide - mass of (p + n +e )
Proton mass: 1.00728 amu
Neutron mass: 1.00867 amu
Electron mass: 0.00055 amu
Massdefect (Dm), then multiply by 931.5 MeV/amu
Chemistry 481, Spring 2015, LA Tech
Chapter-1-15
4. Using the binding energy calculator, calculate the
binding energy 235U if the mass of the this nuclide
(isotope) is 235.0349 amu. ( P= 1.007277 amu, N=
1.008665 amu, e- =0.0005438 amu )
Chemistry 481, Spring 2015, LA Tech
Chapter-1-16
5. What are theories that have been used to describe
the nuclear stability?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-17
Stability of the Elements and Their
Isotopes
P/N Ratio
Why are elements
With Z > 82 are
Unstable?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-18
Magic Numbers
• Nuclei with either numbers of protons or
neutrons equal to Z, N =2 (He), 8(O), 20 (Ca),
28(Si), 50(Sn, 82(Pb), or 126(?)(I)
• exhibit certain properties which are analogous
to closed shell properties in atoms, including
• anomalously low masses, high natural
abundances and high energy first excited
states.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-19
The Kinetics of Radioactive Decay
Nuclear reactions follow 1st order kinetics
Chemistry 481, Spring 2015, LA Tech
Chapter-1-20
6. How long would it take for a sample of 222Rn that
weighs 0.750 g to decay to 0.100 g? Assume a halflife for 222Rn of 3.823 days?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-21
7. The skin, bones and clothing of an adult female
mummy discovered in Chimney Cave, Lake
Winnemucca, Nevada, were dated by radiocarbon
analysis. How old is this mummy if the sample
retains 73.9% of the activity of living tissue?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-22
Bohr model of the atom
Balmer later determined an empirical
relationship that described the spectral lines
for hydrogen.
DE
= - 2.178 x 10-18 m-1
1
= n2
f
(
-
1
n i2
)
nf = 2 ni = 3,4, 5, . . . Blamer series
Spectra of many other atoms can be described by
similar relationships.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-23
Bohr model of the atom
• The Bohr model is a
‘planetary’ type
model.
• Each principal
quantum represents
a new ‘orbit’ or layer.
• The nucleus is at the
center of the model.
• RH = 2.178 x 10-18 J
Chemistry 481, Spring 2015, LA Tech
𝒁𝟐
En = RH 𝟐
𝒏
En =
-
𝒎𝒆𝒁𝟐𝒆𝟒
𝟖𝒉𝟐𝟐𝒏𝟐
Chapter-1-24
Emission Spectrum of Hydrogen
• Bohr studied the spectra produced when atoms were
excited in a gas discharge tube.
He observed that each element produced its
own set of characteristic lines.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-25
Emission Spectrum of Hydrogen
• Line Spectrum
• Energy is absorbed when an electron goes from a
lower(n) to a higher(n)
• Energy is emitted when an electron goes from a
higher(n) to a lower(n) level
• Energy changed is given by:DE = Ef - Ei
• or DE = -2.178 x 10-18 [1/n2f - 1/n2i] J
• DE is negative for an emission and positive for an
absorption
• DE can be converted to l or 1/ l by l = hc/E.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-26
What is Bohr’s Atomic model?
• explain emission spectrum of hydrogen atom
• applied the idea of Quantization to electrons to orbits
• energies of these orbits increase with the distance
from nucleus.
• Energy of the electron in orbit n (En):
• En = -2.178 x 10-18 J (Z2/n2)
• En = -2.178 x 10-18 J 1/n2; Z=1 for H
Chemistry 481, Spring 2015, LA Tech
Chapter-1-27
Bohr model of the atom
Balmer later determined an empirical
relationship that described the spectral lines
for hydrogen.
En =
DE
-
= - 2.178 x 10
𝒎𝒆𝒁𝟐𝒆𝟒
𝟖𝒉𝟐𝟐𝒏𝟐
-18
J
1
(n
f
2
-
1
ni2
)
nf = 2 ni = 3,4, 5, . . . Blamer series
Spectra of many other atoms can be described by
similar relationships.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-28
Paschen, Blamer and Lyman Series
Chemistry 481, Spring 2015, LA Tech
Chapter-1-29
Calculation using the equation:
E = -2.178 x 10-18 (1/nf2 - 1/ni2 ) J, Calculate
the wavelength of light that can excite the
electron in a ground state hydrogen atom to
n = 7 energy level.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-30
Calculation using Bohr eqaution
The energy for the transition from n = 1 to n = 7:
DE = -2.178 x 10-18 J [1/n2f - 1/n2i]; nf = 7, ni = 1
DE = -2.178 x 10-18 [1/72 - 1/12] J
DE = -2.178 x 10-18 [1/49 - 1/1] J
DE = -2.178 x 10-18 [0.02041 - 1] J
DE = -2.178 x 10-18 [-0.97959] J
= 2.134 x 10-18 J (+, absorption)
calculate the l using l = hc/E
6.626 x 10-34 Js x 3.00 x 108 m/s
l = ---------------------2.13 x 10-18 J
l=
9.31 x 10-8 m
Chemistry 481, Spring 2015, LA Tech
Chapter-1-31
8. Using Bohr energy calculator, calculate the
wavelength of light that can excite the electron in a
ground state hydrogen atom from n = 5 to n = 3
energy level.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-32
Wave theory of the electron
• 1924: De Broglie suggested that electrons
have wave properties to account for why their
energy was quantized.
• He reasoned that the electron in the
hydrogen atom was fixed in the space
around the nucleus.
• He felt that the electron would best be
represented as a standing wave.
• As a standing wave, each electron’s
path must equal a whole number times
the wavelength.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-33
De Broglie waves
De Broglie proposed that all particles have a
wavelength as related by:
l =
l
h
m
v
=
=
=
=
Chemistry 481, Spring 2015, LA Tech
h
mv
wavelength, meters
Plank’s constant
mass, kg
frequency, m/s
Chapter-1-34
Constructively Interfered 2D-Wave
Chemistry 481, Spring 2015, LA Tech
Chapter-1-35
destructively Interfered 2D-Wave
Chemistry 481, Spring 2015, LA Tech
Chapter-1-36
Two-dimensional wave - Vibrations on a Drumskin
One circular node
(at the drumskin's edge)
Two circular nodes
(one at the drumskin's edge
plus one more)
Three circular nodes
(one at the drumskin's edge
plus two more)
One transverse node
(plus a circular one at the
drumskin's edge)
Two transverse nodes
(plus one at the drumskin's
edge)
Chemistry 481, Spring 2015, LA Tech
Chapter-1-37
What is a wave-mechanical model?
•
•
•
•
•
motions of a vibrating string shows one dimensional motion.
Energy of the vibrating string is quantized
Energy of the waves increased with the nodes.
Nodes are places were string is stationary.
Number of nodes gives the quantum number.
One
dimensional motion gives one quantum number.
Vibrating String : y = sin(npx/l)
d2y/dx2 = -(n2p2/l2)sin(npx/l) = -(n2p2/l2)y
Chemistry 481, Spring 2015, LA Tech
Chapter-1-38
Quantum model of the atom
• Schrödinger developed an equation to
describe the behavior and energies of
electrons in atoms.
• His equation ( Wave function y) is similar to
one used to describe electromagnetic waves.
Each electron can be described in terms of
Wave function yits quantum numbers. yn, l,
ml, ms),
• y2is proportional probablity of finding the
electron in a given volume. Max Born
Interpretation: y2= atomic orbital
Chemistry 481, Spring 2015, LA Tech
Chapter-1-39
Schrödinger Equation
y = wave function
E = total energy
V = potential energy
Chemistry 481, Spring 2015, LA Tech
Chapter-1-40
Schrödinger Equation
y = wave function E = total energy V = potential energy
Chemistry 481, Spring 2015, LA Tech
Chapter-1-41
Schrödinger Equation in Polar Coordinates
Chemistry 481, Spring 2015, LA Tech
Chapter-1-42
Polar Coordinates
Chemistry 481, Spring 2015, LA Tech
Chapter-1-43
Quantum Model of atom
• Electrons travel in three dimensions
• Four quantum numbers are needed
• three to describe, x, y, z, and four for the spin
• four quantum numbers
describe an orbital currently used to explain the
arrangement, bonding and spectra of atoms.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-44
Four Quantum Numbers of the Atom
• n
value could be
1, 2, 3, 4, 5, 6. 7. . . etc.
• l values depend on n value: can have
0 . . . (n - 1) values
• ml values depends on l value:
can have -l . , 0 . . . +l values of ml
• ms values
should always be -1/2 or +1/2
Chemistry 481, Spring 2015, LA Tech
Chapter-1-45
Solutions to Shrődinger Equation
Series of allowed discrete y values:
yn, l, ml, ms
n = 1,2,3,4,5,6,7..etc.
En = -
Chemistry 481, Spring 2015, LA Tech
𝒎𝒆𝒁𝟐𝒆𝟒
𝟖𝒉𝟐𝟐𝒏𝟐
Chapter-1-46
Components of y
Mathematical expression of hydrogen like orbitals
in polar coordinates:
yn, l, ml, ms (r,,) = R n, l, (r) Y l, ml, (,)
R n, l, (r )
= Radial Wave Function
Y l, ml, (,)
=Angular Wave Function
[R n, l (r )]2 or 4pr2R2 = Radial Distribution
Function or Pnl(r).
Chemistry 481, Spring 2015, LA Tech
Chapter-1-47
Radial Distribution Function, Pnl(r).
This is defined as the probability that an electron in
the orbital with quantum numbers n and l will be
found at a distance r from the nucleus. It is
related to the radial wave function by the
following relationship:
; normalized by
Chemistry 481, Spring 2015, LA Tech
Chapter-1-48
9. Describe the Schrödinger equation and the breaking
up of wave function, y into radial and angular
component of a wave function and explain the general
rule used to find the number of radial and angular
nodes of a wave function.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-49
s-Atomic Orbitals
R n, l, (r) only no Y l, ml, (,)
s orbitals
Chemistry 481, Spring 2015, LA Tech
Chapter-1-50
2s-Atomic Orbital: Probability distribution
ψ2 for the 2s orbital
2s orbital
Chemistry 481, Spring 2015, LA Tech
Chapter-1-51
s-Atomic orbitals
2s
3s
Chemistry 481, Spring 2015, LA Tech
Chapter-1-52
p-Atomic orbitals
2p
3p
Chemistry 481, Spring 2015, LA Tech
Chapter-1-53
Nodes in the y
Total nodes = n -1
Angular nodes = l
Radial nodes = n -1- l
Eg 4d orbital:
Total nodes = 4 -1 = 3
Angular nodes = l = 2
Radial nodes = n -1- l = 4-1-2 = 1
Chemistry 481, Spring 2015, LA Tech
Chapter-1-54
10. Consider the following radial probability
density-distribution plot and respond to the
associated questions.
a) How many radial nodes are there?
b) If the total number of nodes is 3, what type of
orbital is involved?
c) Which orbital would it be if there were one
more node?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-55
.
Radial wavefunctions, Rnl(r), and the radial distribution functions, Pnl(r)
Rnl(r)
Pnl(r)
n
l
1s
1s
1
0
2s
2s
2
0
2p
2p
2
1
3s
3s
3
0
3p
3p
3
1
3d
3d
3
2
Chemistry 481, Spring 2015, LA Tech
Chapter-1-56
d-orbitals
(dxy, dxz, dyz, dz2 , and dx2-y2
orbitals)
Chemistry 481, Spring 2015, LA Tech
Chapter-1-57
f-orbitals
( 4fy3 , 4fx3 , 4fz3 , 4fxz2y2 , 4fyz2x2 , 4fzx2y2 , and 4fxyz orbitals)
Chemistry 481, Spring 2015, LA Tech
Chapter-1-58
Screening (shielding) constant (σ)
Screening (shielding) constant (σ) for each electron
is calculated based on:
the principle quantum number
orbital type and penetration and of all
other electrons in an atom.
σ gives Zeff .
Zeff = Z - σ; Z is the atomic number.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-59
Effective nuclear charge (Zeff)
Zeff is the nuclear charge felt by an electron in a
multielectron atom:
a) Each electron in an atom has different Zeff.
b) Each Zeff is less than atomic number (Z) since
electrons screen each other from the nucleus.
c) Zeff depends on the n and l quantum number of an
electron.
d) Zeff Depends on orbital type the electron is in: Zeff
of 4s > 4p > 4d > 4f.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-60
Radial Wave Funtions
Chemistry 481, Spring 2015, LA Tech
Chapter-1-61
Radial Distribution Functions, Penetration and Shielding
Chemistry 481, Spring 2015, LA Tech
Chapter-1-62
Penetration & Shielding of an Electron in
Multi-electron Atom
Penetration of an electron:
• Greater the penetration there is more chance of
electrons being located close to the nucleus.
• Comparing s, p, d, or f orbitals within same shell (or
principle QN), penetration of an electrons are in the
order: s > p > d > f
Shielding power of an electron:
• Shields of other electrons depends penetration and the
orbital type. Shielding power of electrons in orbitals of
that same shell are: s > p > d > f
Chemistry 481, Spring 2015, LA Tech
Chapter-1-63
Slater Calculation of (Zeff)
Chemistry 481, Spring 2015, LA Tech
Chapter-1-64
Slater Calculation of (Zeff)
Chemistry 481, Spring 2015, LA Tech
Chapter-1-65
11. Cu: (1s2)(2s2, 2p6) (3s2,3p6) (3d10) (4s1) : there
are two possible scenarios for forming Cu+ ionionizing 3d10 electron or 4s1. Using Slater’s Rules
show which one of the electrons 4s or 3d would
come out easily.
If the electron is in a d or f-orbital:
All electrons in groups higher than the electron in question contribute zero to s.
Each electron in the same group contributes 0.35 to s.
All those in groups to the left contribute 1.0 to s
(n-3) (n-2)
(n-1) (n-1)
Cu: (1s2)(2s2, 2p6) (3s2,3p6) (3d10) (4s1)
s(4s1) = ( 10x1 ) ( 8x 0.85)(1X10) = 26.8
Cu: (1s2)(2s2, 2p6) (3s2,3p6) (3d10) (4s1)
s(3d1) = (
18x1
) ( 9x 0.35) (0) = 21.15
Chemistry 481, Spring 2015, LA Tech
Zeff = 29 – 26.6 = 2.4
Zeff = 29 – 21.15 = 7.85
Chapter-1-66
Effective nuclear charge (Zeff) of Atomic
Orbitals vs. Z (atomic number)
En =
Chemistry 481, Spring 2015, LA Tech
-
𝒎𝒆𝒁eff𝟐𝒆𝟒
𝟖𝒉𝟐𝟐𝒏𝟐
Chapter-1-67
How do you get the electronic
configuration of an atom?
• Use periodic table
• Periodic table is divided into orbital blocks
• Each period:
• represents a shell or n
• Start writing electron configuration
• Using following order
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d…
(building up (Auf Bau) principle:)
Chemistry 481, Spring 2015, LA Tech
Chapter-1-68
ELECTRONIC CONFIGURATION OF MANY-ELECTRON
ATOMS
•
AUFBAU (GER. BUILDING UP) PRINCIPLE
•
PAULI EXCLUSION PRINCIPLE
HUND’S RULE
•
Chemistry 481, Spring 2015, LA Tech
Chapter-1-69
Electronic Confn
Li
Be
2s
2s
1
2
H
1s
Na
Mg
3s
3s
1
K
4s
1
2
Sr
5s
5s
2
Cs
Ba
6s
6s
1
2
Fr
Ra
7s
7s
1
1s
N
O
F
2s
2s
2s
2s
2s
2
3s
3s
3s
3s
2
Ni
Cu
3d
2
4s
3d
2
4s
3d
2
4s
3d
1
4s
3d
2
4s
3d
2
4s
3d
2
4s
3d
2
4s
3d
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
4d
2
5s
4d
2
5s
4d
2
5s
4d
1
5s
4d
2
5s
4d
1
5s
4d
1
5s
4d
4d
4d
Lu
Hf
Ta
W
Re
Os
Ir
4f
4f
4f
4f
4f
1
14
1
5d
2
6s
Lr
1
6d
2
7s
2
5
3
14
2
5d
2
6s
5
14
4f
3
5d
2
6s
La
1
5d
2
6s
Ac
1
6d
2
7s
14
4
5d
2
6s
Ce
4f
5
6
5
7
14
5
5d
2
6s
8
14
6
5d
2
6s
1
Pr
Nd
1
4f
4f
3
7
4
4f
4f
Pa
6s
U
Np
2
5f
5f
5f
2
6d
2
7s
Th
6f
7s
Chemistry 481, Spring 2015, LA Tech
2
1
3
1
6d
2
7s
6s
2
6
6s
2
4
Pu
1
5f
6d
2
7s
6
7s
4s
10
Pt
4f
14
9
5d
1
6s
Sm
6s
2
14
Pm
5
10
2
4f
5f
1
Gd
2
5p
10
2
5d
10
6s
2
6p
4d
4d
2
2
5d
10
2
6p
2
5p
Pb
6s
1
5s
2
3
2
6p
4d
2
4
Po
5d
10
6s
3
4
10
5p
10
6s
2
Te
5s
Bi
5d
3d
10
4p
10
4
Se
4s
3
Sb
5p
Tl
2
Sn
5s
1
3d
10
4p
10
3p
As
4s
2
3
2
2
6p
4
2p
5
3p
5
Br
3d
10
4s
2
4p
5
I
4d
10
5s
2
5p
5
At
5d
10
6s
2
6p
5
Tm
Yb
1
4f
4f
4f
4f
4f
4f
6s
2
6s
2
6s
2
12
6s
2
13
6s
2
6s
Es
Fm
Md
No
5f
5f
5f
5f
5f
5f
7s
2
7s
2
11
7s
2
12
7s
2
13
7s
2
3d
10
4s
2
4p
6
Xe
4d
10
5s
2
5p
6
Rn
5d
10
6s
2
6p
14
7s
6
Kr
2
Cf
10
6
2
3p
14
Bk
9
2p
3s
Er
11
2
3s
Ho
10
2s
Ar
2
Dy
9
Ne
Cl
Tb
5d
2
Cm
6s
7
5f
1
6d
2
7s
2
3p
2
4p
2
2
7
2
7s
5s
4f
4f
7
2
6s
1
10
4d
4f
1
2
10
4s
In
14
5d
2
4p
Hg
10
3p
10
10
5s
7
Am
3d
4s
14
6s
6s
Zn
Au
5d
Eu
1
10
5s
7
5d
2
6s
5d
2
6s
2
4f
8
1
4s
Co
4
S
2
Fe
2p
P
2
3d
Mn
3
2
Si
2
3d
Cr
2
2p
10
V
3
2
Ge
Ti
2
2p
Ga
Sc
1
1
2
Al
3p
Rb
1
1
C
2
2p
2
Ca
4s
He
B
2
Chapter-1-70
6
Using the periodic table
• To write the ground-state electron configuration of
an element:
• Starting with hydrogen, go through the elements in
order of increasing atomic number
• As you move across a period
• Add electrons to the ns orbital as you pass through groups
IA (1) and IIA (2).
• Add electrons to the np orbital as you pass through
Groups IIIA (13) to 0 (18).
• Add electrons to (n-1) d orbitals as you pass through IIIB
(3) to IIB(12) and add electrons to (n-2) f orbitals as you
pass through the f -block.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-71
Writing electron configurations
• Electron configurations can also be written
for ions.
• Start with the ground-state configuration for
the atom.
• For cations, remove a number of the
outermost electrons equal to the charge.
• For anions, add a number of outermost
electrons equal to the charge.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-72
Exception to Building Up Principle
a) Electronic Configuration of d-block and f-
block elements
d5 or d10 and f7 or f14 are stable
Cr :[Ar] 3d4 4s2 wrong
Cr :[Ar] 3d5 4s1 correct
Cu :[Ar] 3d9 4s2 wrong
Cu :[Ar] 3d10 4s1 correct
Chemistry 481, Spring 2015, LA Tech
Chapter-1-73
Lanthanoids
La
1
Ce
4f
1
Pr Nd Pm Sm Eu
3
5d
1 4f
2 5d
2
6s
2 6s
6s
4f
4
6s
2
Chemistry 481, Spring 2015, LA Tech
4f
5
6s
2
4f
6
6s
2
4f
7
Gd
4f
7
Tb Dy Ho Er Tm Yb
1
4f
9
4f
10
4f
11
2
2
2
2 5d
6s
6s
6s
2 6s
6s
4f
12
6s
2
4f
13
6s
2
Chapter-1-74
4f
14
6s
2
Actinoids
Ac Th
1
6d
2
7s
6f
2
Pa
U
Np
5f
5f
5f
2
1
2 6d
7s
2
7s
3
1
4
Pu Am
1
5f
6
6d
6d
2
2
2 7s
7s
7s
Chemistry 481, Spring 2015, LA Tech
5f
7
Cm
5f
7
Bk Cf Es Fm Md No
1
5f
9
5f
10
5f
11
2 6d
2
2
2
7s
7s
7s
2 7s
7s
5f
12
7s
2
5f
13
7s
2
Chapter-1-75
5f
14
7s
2
Exception to Building Up Principle
Electronic Configuration of Transition Metal cations
d-block and f-block elements
d orbitals are lower in energy than s orbitals
f orbitals are lower in energy than d orbitals
6
E.g. Neutral atom Fe :[Ar] 3d 4s
3+
5
Cation, Fe :[Ar] 3d
Chemistry 481, Spring 2015, LA Tech
2
Chapter-1-76
12. Give the ground state electronic configurations
of following in core format.
a)
Mo
b)
Ag
c)
V3+
d)
Mn2+
e)
Cr2+
f)
Co3+
g)
Cr6+
h)
Gd3+
Chemistry 481, Spring 2015, LA Tech
Chapter-1-77
Magnetic Properties of Atoms
a) Paramagnetism?
attracted to magnetic field due to un-paired
electrons.
b) Ferromagnetism?
attracted very strongly to magnetic field due to
un-paired electrons.
c) Diamagnetism?
Repelled by a magnetic field due to paired
electrons.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-78
13. Give the ground state electronic configurations
of the following in valence orbital box format and
give the number of unpaired electrons.
a) Mn:
b) Co:
c) Fe2+:
d) Nd3+:
Chemistry 481, Spring 2015, LA Tech
Chapter-1-79
Periodic trends
• Many trends in physical and chemical properties
can be explained by electron configuration.
• We’ll look at some of the more important
examples.
Atomic radii
Ionic radii
First ionization energies
Electron affinities
Chemistry 481, Spring 2015, LA Tech
Chapter-1-80
How does Ionic radii of elements vary?
•
•
•
Cations have smaller radii than neutral
atoms.
Anions have larger radii than neutral atoms
The more charge on the ion more effect on
the radii.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-81
14. How do you measure atomic (ionic)
radii (size)?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-82
Atomic radii of elements going down a group?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-83
Lanthanoide Contration
• Filling of the 4f orbitals in the lanthanides,
which occur within the third series of transition
elements, causes these transition metals to be
smaller than expected because the 4f orbitals
are very poor nuclear shielders and Zeff of 6s2
obitals increase and the atomic radii decrease.
• 3rd-series elements have nearly the same
effective nuclear charge as the 2nd-series
elements, and thus, nearly the same size
Ce [Xe]
Chemistry 481, Spring 2015, LA Tech
1
1
2
4f 5d 6s
Chapter-1-84
15. Why the atomic radius of Zr (1.64) which
is in 5th period is almost similar to a
element, Hf (1.65) in 6th period.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-85
Ionic radii
Cations
These are smaller than the atoms from which
they are formed.
Anions
These are larger than the atoms from which
there are formed..
Chemistry 481, Spring 2015, LA Tech
Chapter-1-86
Isoelectronic configurations
Species that have the same electron
configurations.
Example
Each of the following has an electron
configuration of 1s2 2s2 2p6
O2- FNe
Na+ Mg2+ Al3+
Chemistry 481, Spring 2015, LA Tech
Chapter-1-87
Ionization energy
• First ionization energy
The energy to remove one electron from a
neutral atom in the gas phase.
• A(g) + first ionization energy
A+(g) + e• This indicates how easy it is to form a cation.
Metals tend to have lower first ionization
energies than nonmetals.
• They prefer to become cations.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-88
First
ionization
energy
2500
He
Ne
First ionization energy (kJ/mol)
2000
Ar
1500
Kr
Xe
Rn
1000
500
0
0
20
40
60
80
100
Atomic number
Chemistry 481, Spring 2015, LA Tech
Chapter-1-89
Changes of I.E. Across a period
Chemistry 481, Spring 2015, LA Tech
Chapter-1-90
16. Why is the ionization energy of P (11.00 eV)
greater than S (10.36 eV)?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-91
How does Electron Affinity vary in the
periodic table?
• Electron Affinity depends on Zeff of the nucleus to
the outermost electron in the valence shell.
• Going down the group Zeff for the outer most shell
decrease hence the Electron Affinity also increase
• Going across the period Zeff for the outer most
shell increase hence the Electron Affinity also
decrease
Chemistry 481, Spring 2015, LA Tech
Chapter-1-92
Electron affinity
Chemistry 481, Spring 2015, LA Tech
Atomic number
Chapter-1-93
Electronegativity
The ability of an atom that is bonded to another atom or
atoms to attract electrons to itself.
It is related to ionization energy and electron affinity.
It cannot be directly measured.
The values are unitless since they are relative to each
other.
The values vary slightly from compound to compound
but still provide useful qualitative predictions.
Chemistry 481, Spring 2015, LA Tech
Chapter-1-94
Electronegativities
4
3.5
Electronegativity is a
periodic property.
Electronegativity
3
2.5
2
1.5
1
0.5
0
20
Chemistry 481, Spring 2015, LA Tech
40
Atomic number
60
80
100
Chapter-1-95
17. How you define electronegativity?
Chemistry 481, Spring 2015, LA Tech
Chapter-1-96
Electronegativity Scales
• Pauling Electronegativity, cP
• Mulliken Electronegativity, cM
• The Allred-Rochow, cAR
• Sanderson electronegativity
• Allen electronegativity
Chemistry 481, Spring 2015, LA Tech
Chapter-1-97
Pauling Electronegativity, cP
EA-A and EB-B bond-energy of homonuclear A-A & B-B diatomic molecules
EA-B bond-energy of heteronuclear A-B diatomic molecule
cA cB are electronegativity values of A and B
Pauling comments that it is more accurate to use the geometric mean
rather than the arithmetic mean
Chemistry 481, Spring 2015, LA Tech
Chapter-1-98
Mulliken Electronegativity, cM
The Mulliken electronegativity can only be
calculated for an element for which the electron
affinity is known
• For ionization energies and electron affinities in
electronvolts
• For energies in kilojoules per mole
Chemistry 481, Spring 2015, LA Tech
Chapter-1-99
The Allred-Rochow, cAR
The effective nuclear charge, Zeff experienced by
valence electrons can be estimated using Slater's
rules, while the surface area of an atom in a
molecule can be taken to be proportional to the
square of the covalent radius, rcov. When rcov is
expressed in ångströms,
Chemistry 481, Spring 2015, LA Tech
Chapter-1-100
Sanderson, cs
Sanderson has also noted the relationship between
electronegativity and atomic size, and has
proposed a method of calculation based on the
reciprocal of the atomic volume.
Allen, cA
The simplest definition of electronegativity is that
of Allen, bases on average energy of the valence
electrons in a free atom
where εs,p are the one-
Chemistry 481, Spring 2015, LA Tech
electron energies of s- and
p-electrons in the free atom
and ns,p are the number of
s- and p-electrons in the
valence shell. Chapter-1-101
18. Calculate the electronegativity (X) (Xm, Xar)
for Cl. [ Xm= 1/2(I+Ae);
Xar= 0.744+ 0.359 Zeff/r2 ]
a) Xm When Ei and Eea kJ per mol
Xm= 1.97 x 10-3(1251 + 349 ) + 0.19
Xm = 3.342 (3.54)
a) Xar When r ( 0.99 Angstroms) and Zeff = 6.12
Xar= 0.359 Zeff/r2 + 0.744
Xar = 2.98 (2.83)
Chemistry 481, Spring 2015, LA Tech
Chapter-1-102