Chemistry 120 Thermochemistry Energy Energy is defined as the ability to do work. There are several...

Chemistry 120

Thermochemistry

Energy

Energy is defined as the ability to do work.

There are several forms of energy

Kinetic energy – energy due to motion EK = 1/2mv2

Potential energy – the energy due to the position of a particle in a field

e.g. Gravitational, electrical, magnetic etc.

Chemistry 120

Thermochemistry

Energy

The unit of energy is the Joule (J) and

1 J = 1 kgm2s-2

Thermochemistry is the study of chemical energy and of the conversion of chemical energy into other forms of energy.

It is part of thermodynamics – the study of the flow of heat.

Chemistry 120

Thermochemistry

Thermochemically, we define the system as the part of the universe under study and the surroundings as everything else.

Systems come in three forms:

Open The system can exchange matter and energy with the surroundings

Closed The system can exchange energy only with the surroundings

Isolated There is no exchange of matter or of energy with the surroundings

Chemistry 120

Thermochemistry

Matter is continually in motion and has an internal energy that is composed of several different types

There is

Translation Rotation Vibration Potential

between molecules and inside molecules.

The internal energy is written as U

Chemistry 120

Thermochemistry


There is




The internal energy is directly connected to heat and the transfer of heat.

Chemistry 120

Thermochemistry

Heat is the transfer of internal energy between the surroundings and the system or between systems.

The direction of the heat flow is indicated by the temperature

– heat flows along a Temperature gradient

from high temperature to low temperature.

When the temperature of the system and that of the surroundings are equal, the system is said to be

in thermal equilibrium

Chemistry 120

Thermochemistry

Energy is the capacity to do work

but what is work?

Work is the action of a force over a distance. To be able to do work, we must be able to exert a force over a distance. During this process, energy is expended.

w = F x d

where w is the work, F is the force and d is the distance. Work is measured in Joules.

Chemistry 120

Thermochemistry

PV work

When a gas expands against an external pressure, for example in a cylinder, against a constant weight (weight being a force.....) the work done can be written as

w = F x d

As P = F then F = PA

A

Thus w = PAd

and as Ad = Vfinal – Vinitial = V

Then w = PV

Chemistry 120

Thermochemistry

PV work

By convention, the work done when a gas expands is negative,

Thus

w = - PV

for an expanding gas

Chemistry 120

Thermochemistry

State Functions

The state of a system is defined by the precise conditions of the system:

The quantity and type of matter present

The temperature and pressure

The molecular structure of the system

As 1 mole = 6.02 x 1023 particles, defining the state of a system uniquely is experimentally impossible in an absolute sense.

Chemistry 120

Thermochemistry

State Functions and U

The internal energy, U, of a system is a function of the state of the system.

Although we cannot measure the absolute state of a system, we can measure changes in the state of the system in a relative way, by measuring the work and the heat that takes place during a chemical change.

As U is a function of the state of the system, it does not depend on the way the state of the system is prepared – it is independent of the path.

Chemistry 120

Thermochemistry


U is therefore a state function of the system. It depends only on the present state of the system and not on the previous history or the path by which the system was prepared.

Because we have no measure of the state of a system, or of the internal energy, we can only measure the change in the state, through the observation of work and transfers of heat into and out of the system.

Chemistry 120

Thermochemistry

Energy

Energy is defined as the ability to do work.

There are several forms of energy

Kinetic energy – energy due to motion EK = 1/2mv2

Potential energy – the energy due to the position of a particle in a field

e.g. Gravitational, electrical, magnetic etc.

Chemistry 120

Thermochemistry

Energy

The unit of energy is the Joule (J) and

1 J = 1 kgm2s-2

Thermochemistry is the study of chemical energy and of the conversion of chemical energy into other forms of energy.

It is part of thermodynamics – the study of the flow of heat.

Chemistry 120

Thermochemistry

Thermochemically, we define the system as the part of the universe under study and the surroundings as everything else.

Systems come in three forms:

Open The system can exchange matter and energy with the surroundings

Closed The system can exchange energy only with the surroundings

Isolated There is no exchange of matter or of energy with the surroundings

Chemistry 120

Thermochemistry


There is




Chemistry 120

Thermochemistry


There is




The internal energy is directly connected to heat and the transfer of heat.

Chemistry 120

Thermochemistry

Heat is the transfer of internal energy between the surroundings and the system or between systems.

The direction of the heat flow is indicated by the temperature

– heat flows along a Temperature gradient

from high temperature to low temperature.

When the temperature of the system and that of the surroundings are equal, the system is said to be

in thermal equilibrium

Chemistry 120

Thermochemistry


but what is work?

Chemistry 120

Thermochemistry


but what is work?


w = F x d

where w is the work, F is the force and d is the distance. Work is measured in Joules.

Chemistry 120

Thermochemistry

PV work

When a gas expands against an external pressure, for example in a cylinder, against a constant weight (weight being a force.....) the work done can be written as

w = F x d

As P = F then F = PA

A

Thus w = PAd

and as Ad = Vfinal – Vinitial = V

Then w = PV

Chemistry 120

Thermochemistry

PV work

By convention, the work done when a gas expands is negative,

Thus

w = - PV

for an expanding gas

Chemistry 120

Thermochemistry

State Functions

The state of a system is defined by the precise conditions of the system:

The quantity and type of matter present

The temperature and pressure

The molecular structure of the system

As 1 mole = 6.02 x 1023 particles, defining the state of a system uniquely is experimentally impossible in an absolute sense.

Chemistry 120

Thermochemistry


The internal energy, U, of a system is a function of the state of the system.

Although we cannot measure the absolute state of a system, we can measure changes in the state of the system in a relative way, by measuring the work and the heat that takes place during a chemical change.

As U is a function of the state of the system, it does not depend on the way the state of the system is prepared – it is independent of the path.

Chemistry 120

Thermochemistry


U is therefore a state function of the system. It depends only on the present state of the system and not on the previous history or the path by which the system was prepared.

Because we have no measure of the state of a system, or of the internal energy, we can only measure the change in the state, through the observation of work and transfers of heat into and out of the system.

Chemistry 120

Thermochemistry

Internal Energy, U and State Functions

Energy, and therefore the capacity to do work is present in all matter.

This internal energy is stored in translational, rotational, vibrational and potential forms or modes in the material.

The exact distribution of energy defines the state of the system, together with external variables such as pressure, temperature.

Chemistry 120

Thermochemistry


U is a function of the state of the material only, not of the history of the sample or the path taken to prepare the state of the sample.

Heat is the transfer of energy between the surroundings and the sample

- the symbol for heat is q

Work is the result of a force acting over a distance

- the symbol for work is w

Chemistry 120

Thermochemistry


Heat and work are the only two ways of changing the internal energy of a system.

Temperature is defined by the direction of the flow of heat, which is always from high temperature to low temperature.

When the the temperature of the system and the surroundings are the same, the system is at thermal equilibrium with it’s surroundings.

Chemistry 120

Thermochemistry

The sign conventions of thermochemistry

When the internal energy of the system rises, this energy change has a positive sign.

- The energy of the system rises when heat is absorbed

- The energy of the system rises when work is done on the system e.g. a gas is compressed

- in these cases, q is positive

w is positive

Chemistry 120

ThermochemistryThe sign conventions of thermochemistry

When the internal energy of the system lowers, this energy change has a negative sign.

- The energy of the system lowers when heat is leaves the system

- The energy of the system rises when the system does work e.g. a gas expands against an external pressure

- in these cases, q is negative

w is negative

Chemistry 120

ThermochemistryInternal energy rises:

q > 0

w > 0

Internal energy drops:

q < 0

w < 0

Chemistry 120

ThermochemistryThe First Law of Thermodynamics

Energy can be exchanged but cannot be created or destroyed.

It is a statement of the Law of Conservation of Energy

U = Ufinal – Uinitial = q + w

Chemistry 120

ThermochemistryChemical applications of the 1st Law

Any chemical change can be characterized as an

Endothermic change

or an

Exothermic change.

In an exothermic reaction, internal chemical energy is converted into heat, which leaves the system if the system is not isolated or causes the temperature to rise if the system in isolated.

Chemistry 120

ThermochemistryChemical applications of the 1st Law

In an endothermic reaction, heat is required to drive the chemical reaction and in an isolated system, the temperature will fall. In an non-isolated system, heat is absorbed from the surroundings.

Exothermic T rises (isolated)

q negative (non-isolated)

Endothermic T falls (isolated)

q positive (non-isolated)

Chemistry 120

ThermochemistryReactions at constant pressure and constant volume

At constant volume, V = 0 and so

UV = qV - PV

UV = qV + 0 = qV

When the system can do PV work, i.e. a system at constant pressure,

UP = qP - PV

where w = - PV

Chemistry 120

ThermochemistryMost reactions take place at constant pressure and therefore we define a new function, which is a state function in the same way that U is a state function

Rearranging

UP = qP - PV

UP + PV = qP

We term qP the enthalpy of the reaction

qP = H = UP + PV

Chemistry 120

ThermochemistryEnthalpy is an extensive property – one that depends on the quantity of the material present in the reaction.

This follows directly from the fact that the enthalpy is the heat generated by a reaction

– there is more energy released from 1000 kg of methane when it burns than from 1 g.

Chemistry 120

ThermochemistryEnthalpies and internal energies are measured in kJ mol-1 and the stoichiometry of a reaction is directly applicable to the enthalpy – half the quantity of the reaction results in half the enthalpy change taking place.

Chemistry 120

ThermochemistryWe can characterize reactions as endothermic or exothermic using the enthalpy, H.

If the enthalpy change is negative, the reaction is exothermic and heat is given out by the system

Products

Reactants

H < 0, negative

H

Chemistry 120

ThermochemistryWe can characterize reactions as endothermic or exothermic using the enthalpy, H.

If the enthalpy change is negative, the reaction is endothermic and heat is absorbed by the system

Products

Reactants

H >0, positive

H

Chemistry 120

ThermochemistryUsing the enthalpy, we can account for the heat entering a reaction at constant pressure – in the same way that we account for the products and reactants in a reaction.

In an endothermic reaction, the energy absorbed by the system can be considered as a reactant.

Conversely, an exothermic reaction, one which evolves heat, has the energy as a product.

Chemistry 120

ThermochemistryEnthalpies and internal energies are measured in kJ mol-1 and the stoichiometry of a reaction is directly applicable to the enthalpy – half the quantity of the reaction results in half the enthalpy change taking place.

Chemistry 120

Thermochemistry

Heat Capacities

When a definite quantity of energy is absorbed by materials, the temperature rises.With different materials, the temperature rise, T, is different.

The quantity of energy required to raise a quantity of material by 1 K is termed the heat capacity.

Mathematically,

C = q T

where C is the heat capacity, q is the heat.

Chemistry 120

Thermochemistry

Heat Capacities

The specific heat is the heat per gram of sample and the molar heat capacity is the heat capacity per mole.

Chemistry 120

Thermochemistry

Specific Heats, Molar Heats and Calorimetry

The heat capacity is the quantity of heat required to raise a given quantity of a substance by 1 K

The specific heat 1 gram though 1 K

The molar heat 1 mole through 1 K

The units of heat capacity are

Jg-1K-1 (specific heat) or Jmol-1K-1 (molar heat)

Chemistry 120

Thermochemistry


To calculate the heat transferred to a sample we use

q = quantity x heat capacity x T

For the specific heat

q = mCsT where m = mass

For the molar heat

q = nCmT where n = no. of moles

Make sure that the units of the heat capacity matches the units of quantity that is in the heat equation

Chemistry 120

Thermochemistry


To measure the heat capacity, a calorimeter is used.

A calorimeter measures heat transfers, heats of reaction or heats of dissolution.

Chemistry 120

Thermochemistry


In principle, they consist of an insulated chamber and an accurate way of measuring temperature (a thermocouple or thermometer).

Insulation ensures that the only heat involved in the temperature rise is that inside the calorimeter.

Chemistry 120

Thermochemistry

Heat capacity measurements

A sample with a known temperature is placed into a fluid of known heat capacity and known temperature and allowed to come to thermal equilibrium.

Chemistry 120

Thermochemistry



At thermal equilibrium, Tsample = Tfluid and so we know T for the sample and for the fluid.

Chemistry 120

Thermochemistry




We also know Cfluid and therefore we know qfluid, the heat transferred into the fluid - q = CfluidTfluid

Chemistry 120

Thermochemistry




We also know Cfluid and therefore we know qfluid, the heat transferred into the fluid - q = CfluidTfluid

As this is the only source of heat in the calorimeter, we know qfluid and Tsample, so we can calculate Csample

Chemistry 120

ThermochemistryExample

15.5g of alloy A has a temperature of 98.9 oC. It is placed into a calorimeter containing 25 g of water at 22.5oC. Thermal equilibrium is achieved at 25.7 oC. What is the heat capacity of A?

Chemistry 120


15.5g of alloy A has a temperature of 98.9 oC. It is placed into a calorimeter containing 25 g of water at 22.5 oC. Thermal equilibrium is achieved at 25.7 oC. What is the heat capacity of A? Cwater = 4.18 Jg-1K-1

1. Calculate qwater

2. qwater = - qA from conservation of energy

3. Calculate CA from qA

Chemistry 120



1. Calculate qwater:

Twater = Tfinal – Tinitial = (25.7 – 22.5) oC = 3.2 oC

qwater= 25 x 4.18 x 3.2 = 334 J

Note: qwater is positive as heat is entering the water

Chemistry 120



1. qwater = 334 J

2. qwater = - qA thus qA = - 334 J

Chemistry 120



1. qwater = 334 J


3. qA = mCATA

TA = Tfinal – Tinitial = (25.7 – 98.9) oC = -73.2 oC

Chemistry 120



1. qwater = 334 J


3. qA = mCATA; TA = -73.2 oC

CA = qA/mTA = -334/(15.5 x –73.2) = 0.29 Jg-1K-1

Chemistry 120

Thermochemistry

Bomb Calorimetry

For reactions which generate gas, the PV work makes a significant contribution and the quanitiy we will measure in an open calorimeter is the enthalpy. We cannot easily measure the PV work in this case.

We can measure U in a bomb calorimeter – one where the volume change is zero and therefore V = 0.

The calorimeter is calibrated using a known sample.

Chemistry 120

Thermochemistry

Hess’ Law of Summation

If we wish to determine the heat of reaction or formation of a compound which is not stable, cannot be isolated or cannot be measured for some reason, we use Hess’ Law to determine this quantity.

Hess’ law states that the

the heat of reaction is constant and is not determined by the path of the reaction.

We know this as U (and H) is a state function

Chemistry 120

Thermochemistry


Practically, if we can find a cycle of reactions that is measureable, then we can derive the unmeasurable quantity as we know the total sum of all the energy changes in the cycle.

Chemistry 120

Thermochemistry


Example

The combustion of C results in the formation of CO2 in a bomb calorimeter. The heat of formation

of CO is therefore hard to measure.

We can measure the heat of combustion of CO and that of C both to give CO2.

Chemistry 120

Thermochemistry


Cgraphite + O2 CO + 1/2O2

CO2

Hf(CO)

Hcombustion(CO)Hf(CO2)

Chemistry 120

Thermochemistry


Of the reactions in this cycle, the heats of combustion of CO and C are known, but the heat of formation of CO from C is not.


CO2

Hf(CO)


Chemistry 120

Thermochemistry


Hf(CO2) = Hf(CO) + Hcombustion(CO)


CO2

Hf(CO)


Chemistry 120

Thermochemistry



CO2

Hf(CO)



Hf(CO) = Hf(CO2)- Hcombustion(CO)

Chemistry 120

Thermochemistry


Using the lower equation and the values for the heats of combustion of CO and C, we can calculate the unknown heat in the cycle


CO2

Hf(CO)




Chemistry 120

Thermochemistry




CO2

Hf(CO)


Hf(CO2) = - 393.5 kJ Hcombustion(CO) = - 283.0 kJ

Hf(CO2) = Hf(CO2) - Hcombustion(CO)



Chemistry 120

Thermochemistry




CO2

Hf(CO)


Hf(CO2) = - 393.5 kJ Hcombustion(CO) = - 283.0 kJ

Hf(CO2) = (- 393.5) – (- 283.0) = -110.5 kJ



Chemistry 120

Thermochemistry

Standard enthalpies of formation and reaction

Just as we cannot determine the absolute value for the internal energy of a system and so concentrate on the change in internal energy, so we cannot fix an absolute zero-point for reaction and formation enthalpies.

We chose the Standard state of a material as that at 1 bar pressure (1 bar = 1 x 105 Pa) and the temperature of interest.

Chemistry 120

Thermochemistry


The standard enthalpy of formation of an element in the standard state is defined as zero.

Using these two facts, we can calculate the heats of formation and, through Hess’ cycles, the heats of reaction for all substances.

Chemistry 120

Thermochemistry


When we combine different reactions, we must take account of the stoichiometry of the reaction. Remember that H can be thought of as a product of reaction and must be combine with the correct stoichiometry.

Chemistry 120

Thermochemistry


For the reaction

We can construct a Hess’ cycle:

2NO2 N2O4

Hdimerization(NO2)

Chemistry 120

Thermochemistry


For the reaction

2NO2 N2O4

Hdimerization(NO2)

2NO2 N2O4

Hdimerization(NO2)

1/2N2+ O2

Hf(NO2)1/2Hf(NO2)

We can construct a Hess’ cycle:

Chemistry 120

Thermochemistry


For the reaction

2NO2 N2O4

Hdimerization(NO2)

2NO2 N2O4

Hdimerization(NO2)

1/2N2+ O2

Hf(NO2)1/2Hf(NO2)

We can construct a Hess’ cycle.

Note that we must include the stoichiometry in the calculation.

Chemistry 120

Atomic Structure

Introduction to Quantum Mechanics

Quantum mechanics is the most important scientific and philosphical development in the last 100 years, possibly since Galileo and Newton.

If you are not confused by Quantum Physics then you haven't really understood it.

Niels Bohr

Chemistry 120

Atomic Structure


Web sources:http://phys.educ.ksu.edu/

http://newton.ex.ac.uk/people/jenkins/mbody/mbody2.html

http://www.chembio.uoguelph.ca/educmat/chm386/rudiment/tourquan/tourquan.htm

http://www.upscale.utoronto.ca/GeneralInterest/QM.html

http://www.upscale.utoronto.ca/GeneralInterest/Key/genPHY100.html#THE COURSE CONTENT

Chemistry 120

Atomic Structure


The Players

Sommerfeld

Pauli

Heisenberg

Dirac

Schrödinger

Bohr

Planck

Chemistry 120

Some forms of matter I

Matter comes in many different forms........

Chemistry 120

Some forms of matter II

Matter comes in many different forms........

Chemistry 120

Defects on the surface of copper metal

Impurities in the surface of copper metal

Some forms of matter III

Chemistry 120

Distance to the Horizon 1026 m

Distance to M31 1022 m

Distance to the center of the galaxy 1020 m

Distance to the Nearest Star 1017 m

Distance of Earth to Sun 1011 m

Radius of Sun 108 m

Radius of Earth 106 m

Chemical Basics

Chemistry 120

Radius of Knoxville TN 104 m

A small cow 100 m

Unraveled human DNA strand 10-3 m

Typical size of dust 10-4 m

Typical size of a cell 10 -6 m

(1 micron, 1m)

Chemical Basics

Chemistry 120

Chemical Basics

The Planck Length 10-35 m

Radius of the proton: 10-18 m

Radius of Electron "orbit"

about an atomic nucleus 10-15 m

Wavelength of 1 MeV gamma-ray : 10-12 m

Spacing of atoms in solid copper : 10-10 m

(1 Ångstrom, 1Å)

?

Chemistry 120

Atomic Structure


Classical Mechanics:

All objects move and interact through two forces

Electromagnetic force

Gravity

and the forces obey Newton’s laws of motion.

Electromagnetism obeys Clark Maxwell’s equations

Chemistry 120

Atomic Structure


Classical Mechanics:

Objects have definite trajectories in space.

We understand the position of the object and it’s velocity or momentum.

Energies are continuous and unrestricted.

These objects are large and are in our common experience

Chemistry 120

Atomic Structure


In order to observe a physical event, we must make a measurement of some description

For large objects, this is not a problem but.........

Chemistry 120

Atomic Structure


What happens when how we measure a property of a microscopic object affects the object and changes it?

We can define a large object in an absolute sense as one which is perceptibly unaffected by the measurement.

A small object is one where the measurement chages the object that we measure.

Elephants are large – atoms are small.

Chemistry 120

Atomic Structure


In general, Newton’s laws of motion are applicable to large objects whereas molecules and atoms and objects smaller than these are not.

This fact, combined with the inherent nature of matter and energy on the microscopic scale, that make the quantum world very different from the world of our common experience.

Chemistry 120

Atomic Structure


Continuum energy states are those where there is no restriction on values for the energy of a body.

The color of light is related to the wavelength and therefore the energy – in a continuous spectrum all energies are present

Chemistry 120

Atomic Structure


When atoms are excited, the classically expected continuum spectrum does not appear

Chemistry 120

Atomic Structure


Chemistry 120

Atomic Structure


When a magnetic field or electric field is applied to the gas, the lines split into two, three or more components.

In a magnetic field, this splitting is known as the Zeeman effect

Chemistry 120

Atomic Structure


In an electric field, this splitting is known as the Stark effect

Increasing electric field

Chemistry 120

Atomic Structure


These effects and the discontinuous nature of the spectra are entirely inexplicable using classical mechanics.

A new dynamical and structural description of matter and the interaction of matter with energy was required.

The first model was the Bohr model

Chemistry 120

Atomic Structure

Quantum Mechanics: The Bohr Model

The Bohr model is incorrect but is still shown as the model of the atom today.

It is the model in which electrons orbit the nucleus in a similar way that planets orbit the sun.

The strong central and radial force is provided by the electric force between the nucleus and the electron

Chemistry 120

Atomic Structure

Quantum Mechanics: The Bohr Model

It is the model in which electrons orbit the nucleus in a similar way that planets orbit the sun.

Chemistry 120

Atomic Structure

Quantum Mechanics: The Schrödinger Atom

Erwin Schrödinger improved on the Bohr description and succeeded in explaining the internal dynamics of the atom, revealed by the Stark and Zeeman effects.

The Schrödinger description is based on the wave properties of matter, detailed by Louis de Broglie

Chemistry 120

Atomic Structure

The de Broglie relationship

Louis de Broglie formulated that a particle of momentum p has an associated wavelength

= h p

Where p = mv

Chemistry 120

Atomic Structure

The modern quantum atom

By considering the electron in an atom as a wave, the energy of the electron becomes quantized and gives the correct energy relation that Bohr described empirically by

E= -B n2

and we term n as the principle quantum number

Chemistry 120

Atomic Structure


Classically a particle on a sphere can also move over the surface and this motion is circular. In a similar way, the electron in an atom has properties that we can associate with circular or angular motion.

Electrons in an atom have angular momentum – the momentum that is associated with angular motion

Chemistry 120

Atomic Structure


The angular motion is described by two quantum numbers – l and ml termed the angular quantum

number and the magnetic quantum number respectively.

The electron also has its own angular momentum, called spin s and these four quantum numbers, n, l, ml and s define the properties of the electron in an

atom. They all follow from the wave description of the electron in an atom

Chemistry 120

Atomic Structure


The principle quantum number defines the energy of the electron.

The angular quantum numbers define the shape of the region of space in which the electron is confined – these are termed the orbitals of the atom and they have definite shapes:

Chemistry 120

Atomic Structure

Quantum Mechanics: The Details

The solutions of the Schrödinger wave equations are called wavefunctions and have discrete energies. The solutions are complicated – the Schrödinger equation is

Chemistry 120

Atomic Structure



H = E

Chemistry 120

Atomic Structure



H = E

-ħ2 2 + 2 + 2 + V(x, y, z) = E 2m x2 y2 z2{ }

Chemistry 120

Atomic Structure


The solutions of the Schrödinger wave equations are called wavefunctions and have discrete energies.

The equations are only soluble for the hydrogen atom and give the shapes of the orbitals – the space in which the electron can be found as well as the energies.

Chemistry 120

Atomic Structure


The wavefunctions are characterized and labeled by three quantum numbers,

n the principal quantum number

l the orbital quantum number

ml the magnetic quantum number

The electron also has a quantum number to define its behavior – s the spin quantum number

Chemistry 120

Atomic Structure


The three atomic quantum numbers are connected in terms to the values they can take:

n any integer, except 0

In quantum number n

l is confined to |n –1|

e.g n = 3, l = -2, -1, 0, 1, 2,

There are (2l +1) values for ml

e.g l = 3, ml = -3, -2, -1, 0, 1, 2, 3

Chemistry 120

Atomic Structure


These rules give a maximum number of electrons that can take a value of n

n = 1 2 electrons 2 in l = 0

n = 2 8 electrons 2 in l = 0, 6 in l = 1


10 in l = 2


10 in l = 2, 14 in l = 3

Chemistry 120

Atomic Structure


The orbitals for the hydrogen atom can be calculated explicitly and analytically

n = 1, l = 0

Chemistry 120

Atomic Structure



n = 2, l = 0

Chemistry 120

Atomic Structure



n = 2, l = 1

Chemistry 120

Atomic Structure



n = 3, l = 0

Chemistry 120

Atomic Structure



n = 3, l = 1

Chemistry 120

Atomic Structure


n = 3, l = 2

Chemistry 120

Atomic Structure


n = 4, l = 0

Chemistry 120

Atomic Structure


n = 4, l = 1

Chemistry 120

Atomic Structure


n = 4, l = 2

Chemistry 120

Atomic Structuren = 4, l = 3

Chemistry 120

s block p block1 H

1He2

2 Li3

Be4

B5

C6

N7

O8

F9

Ne10

3 Na11

Mg12

d block Al13

Si14

P15

S16

Cl17

Ar18

4 K19

Ca20

Sc21

Ti22

V23

Cr24

Mn25

Fe26

Co27

Ni28

Cu29

Zn30

Ga31

Ge32

As33

Se34

Br35

Kr36

5 Rb37

Sr38

Y39

Zr40

Nb41

Mo42

Tc43

Ru44

Rh45

Pd46

Ag47

Cd48

In49

Sn50

Sb51

Te52

I53

Xe54

6 Cs55

Ba56

Lu71

Hf72

Ta73

W74

Re75

Os76

Ir77

Pt78

Au79

Hg80

Tl81

Pb82

Bi83

Po84

At85

Rn86

7 Fr86

Ra88

Lr103

Rf104

Db105

Sg106

Bh107

Hs108

Mt109

110 111 112

f blockLa57

Ce58

Pr59

Nd60

Pm61

Sm62

Eu63

Gd64

Tb65

Dy66

Ho67

Er68

Tm69

Yb70

Ac89

Th90

Pa91

U92

Np93

Pu94

Am95

Cm96

Bk97

Cf98

Es99

Fm100

Md101

No102

Atoms, Molecules and Ions

The S block

Chemistry 120

s block p block1 H

1He2

2 Li3

Be4

B5

C6

N7

O8

F9

Ne10

3 Na11

Mg12

d block Al13

Si14

P15

S16

Cl17

Ar18

4 K19

Ca20

Sc21

Ti22

V23

Cr24

Mn25

Fe26

Co27

Ni28

Cu29

Zn30

Ga31

Ge32

As33

Se34

Br35

Kr36

5 Rb37

Sr38

Y39

Zr40

Nb41

Mo42

Tc43

Ru44

Rh45

Pd46

Ag47

Cd48

In49

Sn50

Sb51

Te52

I53

Xe54

6 Cs55

Ba56

Lu71

Hf72

Ta73

W74

Re75

Os76

Ir77

Pt78

Au79

Hg80

Tl81

Pb82

Bi83

Po84

At85

Rn86

7 Fr86

Ra88

Lr103

Rf104

Db105

Sg106

Bh107

Hs108

Mt109

110 111 112

f blockLa57

Ce58

Pr59

Nd60

Pm61

Sm62

Eu63

Gd64

Tb65

Dy66

Ho67

Er68

Tm69

Yb70

Ac89

Th90

Pa91

U92

Np93

Pu94

Am95

Cm96

Bk97

Cf98

Es99

Fm100

Md101

No102


The S block and P block

Chemistry 120

s block p block1 H

1He2

2 Li3

Be4

B5

C6

N7

O8

F9

Ne10

3 Na11

Mg12

d block Al13

Si14

P15

S16

Cl17

Ar18

4 K19

Ca20

Sc21

Ti22

V23

Cr24

Mn25

Fe26

Co27

Ni28

Cu29

Zn30

Ga31

Ge32

As33

Se34

Br35

Kr36

5 Rb37

Sr38

Y39

Zr40

Nb41

Mo42

Tc43

Ru44

Rh45

Pd46

Ag47

Cd48

In49

Sn50

Sb51

Te52

I53

Xe54

6 Cs55

Ba56

Lu71

Hf72

Ta73

W74

Re75

Os76

Ir77

Pt78

Au79

Hg80

Tl81

Pb82

Bi83

Po84

At85

Rn86

7 Fr86

Ra88

Lr103

Rf104

Db105

Sg106

Bh107

Hs108

Mt109

110 111 112

f blockLa57

Ce58

Pr59

Nd60

Pm61

Sm62

Eu63

Gd64

Tb65

Dy66

Ho67

Er68

Tm69

Yb70

Ac89

Th90

Pa91

U92

Np93

Pu94

Am95

Cm96

Bk97

Cf98

Es99

Fm100

Md101

No102


The S block , P block

and D block

Chemistry 120

s block p block1 H

1He2

2 Li3

Be4

B5

C6

N7

O8

F9

Ne10

3 Na11

Mg12

d block Al13

Si14

P15

S16

Cl17

Ar18

4 K19

Ca20

Sc21

Ti22

V23

Cr24

Mn25

Fe26

Co27

Ni28

Cu29

Zn30

Ga31

Ge32

As33

Se34

Br35

Kr36

5 Rb37

Sr38

Y39

Zr40

Nb41

Mo42

Tc43

Ru44

Rh45

Pd46

Ag47

Cd48

In49

Sn50

Sb51

Te52

I53

Xe54

6 Cs55

Ba56

Lu71

Hf72

Ta73

W74

Re75

Os76

Ir77

Pt78

Au79

Hg80

Tl81

Pb82

Bi83

Po84

At85

Rn86

7 Fr86

Ra88

Lr103

Rf104

Db105

Sg106

Bh107

Hs108

Mt109

110 111 112

f blockLa57

Ce58

Pr59

Nd60

Pm61

Sm62

Eu63

Gd64

Tb65

Dy66

Ho67

Er68

Tm69

Yb70

Ac89

Th90

Pa91

U92

Np93

Pu94

Am95

Cm96

Bk97

Cf98

Es99

Fm100

Md101

No102


The S block , P block ,

D block and F block

Chemistry 120

Atomic Structure

The Aufbau Principle and the Periodic Table

The quantum mechanical rules the relate n, l and ml

dictate the structure of the periodic table through the

aufbau prinicple, when used in conjunction with the

Exclusion principle

The rules are that, given n,

l = n – 1 and ml = +/- l including 0

Chemistry 120

Atomic Structure


For each value of n, l ml there are two possibilities

for s the spin of the electron - + ½ and - ½.

Each orbital can therefore accommodate two and

only two electrons.

We can therefore write the electronic configurations

of the atoms in terms of the occupations of each

orbital.

Chemistry 120

Atomic Structure


For hydrogen,

n = 1, l = n – 1= 0 and ml = 0.

The only possibilities are therefore ± ½ and we write

that H has a configuration of 1s2, showing the

prinicipal quantum number, the l quantum number

and the number of electrons.

Chemistry 120

Atomic Structure


All the orbitals that we can calculate from the

Schrödinger equation are hydrogenic as we can only

solve the Schrödinger equation for a two particle

system.

In hydrogen all the orbitals with the same n with

non-zero l and ml have the same energies, the only

energy differences between orbitals being n. Such

orbitals are termed degenerate.

Chemistry 120

Atomic Structure


In atoms heavier than hydrogen, the l quantum

number does effect the energy slightly and the

orbitals are no longer degenerate. This becomes

more important for heavier atoms and effects the

order of filling in the periodic table.

Chemistry 120

Atomic Structure


A second and highly important factor is the

distribution of the electrons with in the atom.

Any orbital with non-zero l has an angular node that

runs through the nucleus – the density of the

electrons at the nucleus is zero for these orbitals.

s orbitals have density at the nucleus and the force

on these from the nucleus is higher, so they are more

strongly bound

Chemistry 120

Atomic Structure


In general, the higher l the less penetrating the

orbitals are and the order of filling is

s before p before d before f

Anomalies appear at the 3d sub-shell. After Ar (3p6),

the 4s shell fills first, before the 3d. A similar feature

occurs before the filling of the 4f shell.

Chemistry 120

Atomic Structure


Hund’s rule is the final rule for the configuration of the atom.

Orbitals are filled such that all spins are parallel and all orbitals are singly filled first, before doubling filling the orbitals with paired spins.

Spin-parallel electrons cannot occupy the same space and so the repulsion between electrons is reduced. Spin-paired electrons can occupy the same region of space and the repulsion is higher.

Chemistry 120

s block p block1 H

1He2


Building the Periodic Table

Chemistry 120


Building the Periodic Tables block p block1 H

1He2

2 Li3

Be4

B5

C6

N7

O8

F9

Ne10

Chemistry 120

s block p block1 H

1He2

2 Li3

Be4

B5

C6

N7

O8

F9

Ne10

3 Na11

Mg12

Al13

Si14

P15

S16

Cl17

Ar18


Building the Periodic Table

Chemistry 120

s block p block1 H

1He2

2 Li3

Be4

B5

C6

N7

O8

F9

Ne10

3 Na11

Mg12

d block Al13

Si14

P15

S16

Cl17

Ar18

4 K19

Ca20

Sc21

Ti22

V23

Cr24

Mn25

Fe26

Co27

Ni28

Cu29

Zn30

Ga31

Ge32

As33

Se34

Br35

Kr36


The Periodic Table

Chemistry 120

s block p block1 H

1He2

2 Li3

Be4

B5

C6

N7

O8

F9

Ne10

3 Na11

Mg12

d block Al13

Si14

P15

S16

Cl17

Ar18

4 K19

Ca20

Sc21

Ti22

V23

Cr24

Mn25

Fe26

Co27

Ni28

Cu29

Zn30

Ga31

Ge32

As33

Se34

Br35

Kr36

5 Rb37

Sr38

Y39

Zr40

Nb41

Mo42

Tc43

Ru44

Rh45

Pd46

Ag47

Cd48

In49

Sn50

Sb51

Te52

I53

Xe54


The Periodic Table

Chemistry 120

s block p block1 H

1He2

2 Li3

Be4

B5

C6

N7

O8

F9

Ne10

3 Na11

Mg12

d block Al13

Si14

P15

S16

Cl17

Ar18

4 K19

Ca20

Sc21

Ti22

V23

Cr24

Mn25

Fe26

Co27

Ni28

Cu29

Zn30

Ga31

Ge32

As33

Se34

Br35

Kr36

5 Rb37

Sr38

Y39

Zr40

Nb41

Mo42

Tc43

Ru44

Rh45

Pd46

Ag47

Cd48

In49

Sn50

Sb51

Te52

I53

Xe54

6 Cs55

Ba56

Lu71

Hf72

Ta73

W74

Re75

Os76

Ir77

Pt78

Au79

Hg80

Tl81

Pb82

Bi83

Po84

At85

Rn86

f blockLa57

Ce58

Pr59

Nd60

Pm61

Sm62

Eu63

Gd64

Tb65

Dy66

Ho67

Er68

Tm69

Yb70


The Periodic Table

Chemistry 120

s block p block1 H

1He2

2 Li3

Be4

B5

C6

N7

O8

F9

Ne10

3 Na11

Mg12

d block Al13

Si14

P15

S16

Cl17

Ar18

4 K19

Ca20

Sc21

Ti22

V23

Cr24

Mn25

Fe26

Co27

Ni28

Cu29

Zn30

Ga31

Ge32

As33

Se34

Br35

Kr36

5 Rb37

Sr38

Y39

Zr40

Nb41

Mo42

Tc43

Ru44

Rh45

Pd46

Ag47

Cd48

In49

Sn50

Sb51

Te52

I53

Xe54

6 Cs55

Ba56

Lu71

Hf72

Ta73

W74

Re75

Os76

Ir77

Pt78

Au79

Hg80

Tl81

Pb82

Bi83

Po84

At85

Rn86

7 Fr86

Ra88

Lr103

Rf104

Db105

Sg106

Bh107

Hs108

Mt109

110 111 112

f blockLa57

Ce58

Pr59

Nd60

Pm61

Sm62

Eu63

Gd64

Tb65

Dy66

Ho67

Er68

Tm69

Yb70

Ac89

Th90

Pa91

U92

Np93

Pu94

Am95

Cm96

Bk97

Cf98

Es99

Fm100

Md101

No102


The Periodic Table

Chemistry 120

Atomic Structure

Periodic Trends

As the number of electrons in an atom rises, the size of the atom increases.

As the binding energy of the electrons rises, the size of the atom decreases.

These two factors mean that the size of the atom increases right to left and top to bottom in the Periodic Table. Cs is the largest stable atom and F the smallest.

Chemistry 120

Atomic Structure

Periodic Trends

Ionic radii also follow the same trends.

Cations are smaller than the neutral atoms and anions are larger than the neutral atoms, though the trend in ion sizes follow those of the atoms.

Chemistry 120

Atomic Structure

Periodic Trends

The energy required to remove electrons from the atoms is termed the ionization energy.

In breaking a subshell there is a large jump in ionization energy.

In breaking a shell, there is a huge jump in ionization energy.

Chemistry 120 Thermochemistry Energy Energy is defined as the ability to do work. There are several...

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Transcript of Chemistry 120 Thermochemistry Energy Energy is defined as the ability to do work. There are several...