Chemistry 481(01) Spring 2016 - Louisiana Tech Universityupali/chem481/slides/HW#1-chem481-chapter-1.pdf · May 17, 2016: Test 3 ... May 18, Make Up: Comprehensive covering all Chapters

Chapter-1-1Chemistry 481, Spring 2016, LA Tech

Instructor: Dr. Upali Siriwardane

e-mail: [email protected]: 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 5 , 2016: Test 1 (Chapters 1, 2, 3, 4)

April 28, 2016: Test 2 (Chapters (6 & 7)

May 17, 2016: Test 3 (Chapters. 19 & 20)

May 18, Make Up: Comprehensive covering all Chapters

Chemistry 481(01) Spring 2016


Origin of Elements in the UniverseScientists 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).


Predicted Nuclear Fusion of

Light Elements in the Young,

Hot Universe


Few minutes after big Bang


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


Nuclear

Burning


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.


1. What are the two basic types of nuclear

reactions? Give examples of each that occur during

the formation of the Universe


Cosmic Abundances


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.)



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?



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?


3. Predict the most likely modes of decay and the

products of decay of the following nuclides:17F:

105Ag:

185Ta:


Bonding Energy Curve


Nuclear Binding EnergyThe 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


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 )


5. What are theories that have been used to describe

the nuclear stability?


Stability of the Elements and Their

Isotopes

P/N Ratio

Why are elements

With Z > 82 are

Unstable?


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.


The Kinetics of Radioactive Decay

Nuclear reactions follow 1st order kinetics


6. How long would it take for a sample of 222Rn that

weighs 0.750 g to decay to 0.100 g? Assume a half-

life for 222Rn of 3.823 days?


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?


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

nf2

1

ni2-

nf = 2 ni = 3,4, 5, . . . Blamer series

Spectra of many other atoms can be described by

similar relationships.



• 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 En = -𝒎

𝒆𝒁𝟐𝒆𝟒

𝟖𝒉𝟐𝟐𝒏𝟐

En = RH

𝒁𝟐

𝒏𝟐


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.


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/n2

i] 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.


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



Balmer later determined an empirical

relationship that described the spectral lines

for hydrogen.

DE = - 2.178 x 10-18

J ( )1

nf2

1

ni2-

nf = 2 ni = 3,4, 5, . . . Blamer series

Spectra of many other atoms can be described by

similar relationships.

En = -𝒎


𝟖𝒉𝟐𝟐𝒏𝟐


Paschen, Blamer and Lyman Series


Calculation using the equation:

E = -2.178 x 10-18 (1/nf2 - 1/ni

2 ) J, Calculate

the wavelength of light that can excite the

electron in a ground state hydrogen atom to

n = 7 energy level.


The energy for the transition from n = 1 to n = 7:

DE = -2.178 x 10-18 J [1/n2f - 1/n2

i]; 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/sl = ----------------------

2.13 x 10-18 J

l = 9.31 x 10-8 m

Calculation using Bohr eqaution


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.


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.


De Broglie proposed that all particles have a

wavelength as related by:

l = wavelength, meters

h = Plank’s constant

m = mass, kg

v = frequency, m/s

De Broglie waves

l =h

mv


Constructively Interfered 2D-Wave


destructively Interfered 2D-Wave


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)


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


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 yits quantum numbers. yn, l,

ml, ms),

• y2is proportional probablity of finding the

electron in a given volume. Max Born

Interpretation: y2= atomic orbital


Schrödinger Equation

y = wave function

E = total energy

V = potential energy


Schrödinger Equation

y = wave function E = total energy V = potential energy


Schrödinger Equation in Polar Coordinates


Polar Coordinates


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.


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


Solutions to Shrődinger Equation

Series of allowed discrete y values:

yn, l, ml, ms

n = 1,2,3,4,5,6,7..etc.

En = -𝒎


𝟖𝒉𝟐𝟐𝒏𝟐


Components of y

Mathematical expression of hydrogen like orbitals

in polar coordinates:

yn, 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).


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


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.


s orbitals

R n, l, (r) only no Y l, ml, (,)

s-Atomic Orbitals


2s orbital

2s-Atomic Orbital: Probability distribution

ψ2 for the 2s orbital


2s

3s

s-Atomic orbitals


p-Atomic orbitals

2p

3p


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


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?


.

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

Radial wavefunctions, Rnl(r), and the radial distribution functions, Pnl(r)


d-orbitals(dxy, dxz, dyz, dz

2 , and dx2-y

2

orbitals)


f-orbitals( 4fy3 , 4fx3 , 4fz3 , 4fxz2y2 , 4fyz2x2 , 4fzx2y2 , and 4fxyz orbitals)


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.


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.


Radial Wave Funtions


Radial Distribution Functions, Penetration and Shielding


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


Slater Calculation of (Zeff)


Slater Calculation of (Zeff)


11. Cu: (1s2)(2s2, 2p6) (3s2,3p6) (3d10) (4s1) : there

are two possible scenarios for forming Cu+ ion-

ionizing 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 Zeff = 29 – 26.6 = 2.4

Cu: (1s2)(2s2, 2p6) (3s2,3p6) (3d10) (4s1)

s(3d1) = ( 18x1 ) ( 9x 0.35) (0) = 21.15 Zeff = 29 – 21.15 = 7.85


Effective nuclear charge (Zeff) of Atomic

Orbitals vs. Z (atomic number)

En = - 𝒎𝒆𝒁eff

𝟐𝒆𝟒

𝟖𝒉𝟐𝟐𝒏𝟐


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:)


ELECTRONIC CONFIGURATION OF MANY-ELECTRON

ATOMS

• AUFBAU (GER. BUILDING UP) PRINCIPLE

• PAULI EXCLUSION PRINCIPLE

• HUND’S RULE


Tl

5d10

6s2

6p1

Hg

4f14

5d10

6s2

Au

4f14

5d10

6s1

Hf

4f14

5d2

6s2

Lu

4f14

5d1

6s2

Li

2s1

Na

3s1

Cs

6s1

Rb

5s1

K

4s1

Fr

7s1

Pt

4f14

5d9

6s1

Ir

4f14

5d7

6s2

Os

4f14

5d6

6s2

Re

4f14

5d5

6s2

W

4f14

5d4

6s2

Ta

4f14

5d3

6s2

H

1s1

He

1s2

Rn

5d10

6s2

6p6

At

5d10

6s2

6p5

Po

5d10

6s2

6p4

Bi

5d10

6s2

6p3

Pb

5d10

6s2

6p2

Cd

4d10

5s2

Ag

4d10

5s1

Zr

4d2

5s2

Y

4d1

5s2

Pd

4d10

Rh

4d8

5s1

Ru

4d7

5s1

Tc

4d5

5s2

Mo

4d5

5s1

Nb

4d3

5s2

Lr

6d1

7s2

Ba

6s2

Be

2s2

Mg

3s2

Sr

5s2

Ca

4s2

Ra

7s2

Zn

3d10

4s2

Cu

3d10

4s1

Ti

3d2

4s2

Sc

3d1

4s2

Ni

3d8

4s2

Co

3d7

4s2

Fe

3d6

4s2

Mn

3d5

4s2

Cr

3d5

4s1

V

3d3

4s2

In

4d10

5s2

5p1

Xe

4d10

5s2

5p6

I

4d10

5s2

5p5

Te

4d10

5s2

5p4

Sb

4d10

5s2

5p3

Sn

4d10

5s2

5p2

Ga

3d10

4s2

4p1

Kr

3d10

4s2

4p6

Br

3d10

4s2

4p5

Se

3d10

4s2

4p4

As

3d10

4s2

4p3

Ge

3d10

4s2

4p2

Al

3s2

3p1

Ar

3s2

3p6

Cl

3s2

3p5

S

3s2

3p4

P

3s2

3p3

Si

3s2

3p2

B

2s2

2p1

Ne

2s2

2p6

F

2s2

2p5

O

2s2

2p4

N

2s2

2p3

C

2s2

2p2

Gd

4f7

5d1

6s2Cm

5f7

6d1

7s2

Tb

4f9

6s2

Bk

5f9

7s2

Sm

4f6

6s2

Pu

5f6

7s2

Eu

4f7

6s2

Am

5f7

7s2

Nd

4f4

6s2

U

5f3

6d1

7s2

Pm

4f5

6s2

Np

5f4

6d1

7s2

Ce

4f1

5d1

6s2

Th

6f2

7s2

Pr

4f3

6s2

Pa

5f2

6d1

7s2

Yb

4f14

6s2

No

5f14

7s2

La

5d1

6s2

Ac

6d1

7s2

Er

4f12

6s2

Fm

5f12

7s2

Tm

4f13

6s2

Md

5f13

7s2

Dy

4f10

6s2

Cf

5f10

7s2

Ho

4f11

6s2

Es

5f11

7s2

Electronic Confn


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.


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.


Exception to Building Up Principle

a) Electronic Configuration of d-block and f-

block elements

d5 or d10 and f7 or f14 are stableCr :[Ar] 3d4 4s2 wrong

Cr :[Ar] 3d5 4s1 correct

Cu :[Ar] 3d9 4s2 wrong

Cu :[Ar] 3d10 4s1 correct


Lanthanoids

Gd

4f7

5d1

6s2

Tb

4f9

6s2

Sm

4f6

6s2

Eu

4f7

6s2

Nd

4f4

6s2

Pm

4f5

6s2

Ce

4f1

5d1

6s2

Pr

4f3

6s2

Yb

4f14

6s2

La

5d1

6s2

Er

4f12

6s2

Tm

4f13

6s2

Dy

4f10

6s2

Ho

4f11

6s2


Actinoids

Cm

5f7

6d1

7s2

Bk

5f9

7s2

Pu

5f6

7s2

Am

5f7

7s2

U

5f3

6d1

7s2

Np

5f4

6d1

7s2

Th

6f2

7s2

Pa

5f2

6d1

7s2

No

5f14

7s2

Ac

6d1

7s2

Fm

5f12

7s2

Md

5f13

7s2

Cf

5f10

7s2

Es

5f11

7s2


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

E.g. Neutral atom Fe :[Ar] 3d6

4s2

Cation, Fe3+

:[Ar] 3d5

Exception to Building Up Principle


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+


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.


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+:


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


• 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.

How does Ionic radii of elements vary?


14. How do you measure atomic (ionic)

radii (size)?


Atomic radii of elements going down a group?


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] 4f1

5d1

6s2


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.


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..


Isoelectronic configurations

Species that have the same electron

configurations.

Example

Each of the following has an electron

configuration of 1s2 2s2 2p6

O2- F- Ne

Na+ Mg2+ Al3+


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.


0

500

1000

1500

2000

2500

0 20 40 60 80 100

First ionization energyHe

Ne

Ar

Kr

Xe

Rn

Fir

st

ion

iza

tio

n e

ne

rgy

(k

J/m

ol)

Atomic number


Changes of I.E. Across a period


16. Why is the ionization energy of P (11.00 eV)

greater than S (10.36 eV)?


• 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

How does Electron Affinity vary in the

periodic table?


Electron affinity

Atomic number


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.


Electronegativities

0.5

1

1.5

2

2.5

3

3.5

4

0 20 40 60 80 100

Ele

ctr

on

eg

ati

vit

y

Atomic number

Electronegativity is a

periodic property.

Electronegativity is a

periodic property.


17. How you define electronegativity?


Electronegativity Scales

• Pauling Electronegativity, cP

• Mulliken Electronegativity, cM

• The Allred-Rochow, cAR

• Sanderson electronegativity

• Allen electronegativity


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


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


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,

http://en.wikipedia.org/wiki/Valence_electron

http://en.wikipedia.org/wiki/Slater's_rules

http://en.wikipedia.org/wiki/Covalent_radius

http://en.wikipedia.org/wiki/%C3%85ngstr%C3%B6m


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.

The simplest definition of electronegativity is that

of Allen, bases on average energy of the valence

electrons in a free atom

Allen, cA

where εs,p are the one-

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.

http://en.wikipedia.org/wiki/Valence_electron


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)

Documents

Chemistry 481(01) Spring 2016 - Louisiana Tech Universityupali/chem481/slides/HW#1-chem481-chapter-1.pdf · May 17, 2016: Test 3 ... May 18, Make Up: Comprehensive covering all Chapters