Physical Chem Notes

8/2/2019 Physical Chem Notes

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Physical Chem Notes 6th Apr,2012

A. Electron

Energy

2. quantized energy

3. Bohrs model

1. For H

2. +1C nucleus

3. Orbits with discrete energy

4. excited statestransitionrelease of energy (i.e. light or heat)

5. determine I.E. (convergence limit) from atomic spectrum---v/v

2. Electron shell (allowed energy lv.)

- successive I.E.

- 1st I.E. of period

- 2,3,3 pattern

- orbitals---s, p, d.

3. Electron configuration

Successive I.E.

Aufbau Principle Pauli exclusion principle

Hunds rule (mutual repulsion)

4. Electron attraction/ repulsion

Shielding effect

Distance/ size

Extra stability (uniform distribution of Q)

Mutual repulsion Effective nuclear charge (no. of proton)

atomic & ionic radii, electronegativity, I.E.

5. Electron distribution

Uniform stable

Minimum repulsion stable

Non uniform in bonding polarity dipole inter- forces


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B. System

1. Nature

1. System is formed lower energy ( from cluster of e) arrangement

energetically

2. Each system has both attraction & repulsion

3. Ionic ---big in electronegativity---transfer of electron

4. Covalent ---electron cloud overlapping (localized/ delocalised)-----small

E-vity

5. Metallic better shielding effect, delocalized

6. Strength of bonding atomic/metallic/covalent radii + no. of bonding

electrons

7. Octet rule

2. Physical prop of metallic structure

1. M.p---only weakening2. High B.P.----as all broken

3. Ductility & malleability----mobility of electrons

4. Conductivity ------mobile electrons---------one in, one out // hot cool

5. Shiny ----- close Elv. absorb & re-emit all

3. Packing in metals

1. Min. volume, max. lattice stability( ~Elv.) min energy content

2. CCP(74%)

3. HCP

Electronegativity Electron affinity

In a bond Addition of an e

Attraction on bonding e Repulsion is considered

Accounts for polarityRelated to bond length strength

Octahedral & tetrahedral holes (mutually exclusive)


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4. BCC(6 8%)

5. Coordination no.- packing efficiency

6. Packing close more planes for deformation

4. Packing in ionic crystals

1. *greatest contact between opp. Q

2. Pattern depends on relative size of ions

5. Covalent bonding

1. Bonding environment

Bond angle, hybridization, no. of bond pairs& lone pairs

If repulsion + short bond length efficiency of overlapping

High-s-character overlapping - higher bond strength---bond

enthalpy

Smaller size of orbitals- high degree of overlapping

2. Violation of octet rule----expansion of octet if Elv.s are close in energy

3. Formation of bond and shape

Valence bond theory + Octet rule

I. Covalent bond from overlapping of orbitals (sharing or dative)

VSEPR theoryI. LP-LP>LP-BP>BP-BP

Theory of hybridization---- delocalization

I. Separate orbitals mix to give a new set of hybrid orbitals

II. Determine no. of bonds & shape

III. Purpose: more unpaired e- extra bonds----stable

E(excitation) < E(released from extra bonds)

IV. Paired orbitals have little participation in bonding

V. Types

VI. For delocalizationcoplanar

4. Packing efficiency (esp. macromoleculesshort v.d.f.)

Symmetry

Regularity

Rotation

1. sp One s + one p S character: 50%

2. sp2 One s + two p 33.33333%

3. sp3 One s + three p 25%

NB: Increase in s characterdegree of overlappingcloser bonding ebond strength


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6. Bonding intermediate

7. Inter-force

1. DD

2. London dispersion forces

3. H-bond-----------------ENTROPY DECREASE for INTRA- H-bond

4. **state of matter( solid liquid or gas)

Inter-forces

KE translational motion

C. Energy

1. definition

1. chemical energy due to breaking/forming of interactions

2. exothermic lower E content VS endo-

2. key terms1. 1st law of thermodynamics

Conservation of energy

i.e. Hsurr= -Hsys

H= change in heat content

More veenergetically more favourable

2. 2nd law of thermodynamics

Stotal= Ssys +Ssurr>0

S = in disorderness

S= no of ways to spread energy out (over more quantized Elv.

(1) Ionic-polarising power size-1

charge-polarisablity size charge

(2) Covalent- in Electro-ve-vector sum of dipole moments

(universal)


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less repulsion

3. Hesss law

H is independent of the reaction pathways taken

4. Stable

Reference to ..

Kinetically/ Energetically

5. Spontaneous (feasibility)

instantaneous

=one way route

=may need a push to overcome energy barrier

6. Gibbs Law

G


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Mechanism : molecularity

5. expt. procedures

known volume or molarity

indication of time

control of variables

6. collision theory

must collide to react

right KE and orientation

rate collision freq.

7. Catalyst

Alternative pathway

Effective

Regenerative

Specific

I. Heterogeneous

Low lying vacant d orbital adsorption till satuation

Concentrate and provide right orientation

Weak interaction desorbs easily

Stereospecific

II. Homogeneous

Various O.S.

Intermediate compounds

Physical Chem Notes

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