Chemical bonding and different types of interactions

different types of interactions- ionic bond, covalent bond, metallic bond, hydrogen bond, Van der Waals

1. Department of Physics, M.E.S Ponnani College
K. Muhammed Abdurahman

2. Energies of Interactions Between Atoms
Ionic bonding
What kind of forceshold the atoms together in a solid?
Ionic bonding
Covalent bonding
Metallic bonding
Van der waals bonding
Hydrogen bonding
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3. Energies of InteractionsBetween Atoms
•Theenergyofthecrystalislowerthanthatofthefree
atomsbyanamountequaltotheenergyrequiredto
pullthecrystalapartintoasetoffreeatoms.
•Binding(cohesive)energyofthecrystal.
–NaCl is more stable than a collection of free Na and Cl.–NaCl is more stable than a collection of free Na and Cl.
–Ge crystal is more stable than a collection of free Ge.
Cl Na NaCl
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4. Interactions
Or bonds
Primary
bonds
Secondary
bonds
Van der
Ionic Covalent Metallic
Van der
waals
Hydrogen
All bonding is a consequence of the electrostatic
interaction between the nuclei and electrons.
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5. SI. No:Bond Example Nature of interaction
1. Ionic NaCl Transfer of valence electrons
2. Covalent Diamond Sharing electrons
Types of Bonding Mechanisms
2. Covalent Diamond Sharing electrons
3. Metallic Ag, CuFreeelectrons
4.
Van der
Waals
N –solid
Electrons remainsassociated
with original molecule.
5. Hydrogen Ice -
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6. IONIC BONDINGIONIC BONDING
Ionicbondingistheelectrostaticforceof
attractionbetweenpositivelyandnegatively
chargedions(betweennon-metalsandmetals).
AllioniccompoundsarecrystallinesolidsatAllioniccompoundsarecrystallinesolidsat
roomtemperature.
NaClisatypicalexampleofionicbonding.
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7. •Metallicelementshavevalenceelectronsintheiroutershell.
•Whenlosingtheirelectronstheybecomepositiveions.
•Electronegativeelementstendtoacquireadditionalelectronsto
becomenegativeionsoranions.
Na Cl
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8. •Transfer of electron
•Electro positive and electro negative
•Coulomb attractive force
•After interaction: Similar to inert gas –symmetric
charge distribution
•Cohesive energy –5 to 10 eV
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9. •WhentheNa
+
andCl
-
ionsapproacheachotherclosely
enoughsothattheorbitsoftheelectronintheionsbeginto
overlapwitheachother,thentheelectronbeginstorepel
eachotherbyvirtueoftherepulsiveelectrostaticcoulomb
force.
•Topreventaviolationoftheexclusionprinciple,thecloser
togethertheions,thenthepotentialenergyofthesystem
increasesveryrapidlyresultingalargerepulsiveforce
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10. Na –1S
2
2S
2
2P
6
3S
1
Na
+
–2P
6 Ne
Cl –1S
2
2S
2
2P
6
3S
2
3P
5
Cl
–
–3P
6
Ar
•Na
+
surrounded by six Cl
–
and vice versa
•Binding energy = 7.8 eV
•Eg:-KCl, Al
2O
3, etc
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11. COVALENT BONDINGCOVALENT BONDING
•Takesplacebetweenatomswithsmalldifferencesinelectro
negativitywhichareclosetoeachotherintheperiodictable
(betweennon-metalsandnon-metals).
•Thecovalentbondingisformedwhentheatomssharethe
outershelle
–
(i.e.,sandpe
–
)ratherthanbye
–
transfer.
•Noblegaselectronconfigurationcanbeattained.•Noblegaselectronconfigurationcanbeattained.
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13. •Eache
–
inasharedpairisattractedtobothnucleiinvolvedin
thebond.
•e
–
overlapandattractionofnucleus(proton)ande
–
ina
hydrogenmolecule.
e
e
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15. •Examples: Cl
2, H
2O, O
2, N
2, …….
•Sharing of electron
•Total potential energy, U decreases
•Orbitals overlap effectively
•Orbitals are directionally oriented rather
than spherical symmetric.
•p-orbitalsare directional
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16. Diamond
•Carbon atom, C –1s
2
2s
2
2p
2
•Modified to –1s
2
2s
1
2p
x
1
2p
y
1
2p
z
1
since 2s& 2p–energy levels are closer
•4 unpaired electrons –4 covalent bonds -equal strength•4 unpaired electrons –4 covalent bonds -equal strength
•C-C-C bond angle is 109
0
28’
•C –is sp
3
hybridized & form tetrahedron
•Each tetrahedron is covalently bonded to 4 tetrahedron
–form a 3D network shape.
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17. Properties
•Strong bond
•Binding Energy of C = 7.4 eV
•Very hard and brittle•Very hard and brittle
•High Melting and Boiling points
•Poor conductor (but resistivity increases
as temperature increases)
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18. Comparison of Ionic and Covalent BondingComparison of Ionic and Covalent Bonding
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19. METALLIC BONDINGMETALLIC BONDING
•Metallic bonding is found in metal
elements.
•Partial sharing of valence electrons
•electrostatic force of attraction
between positively charged ions and between positively charged ions and
delocalizedouter electrons.
•Atoms contribute valence electrons
to a common pool.
•Free electron cloud or gas
+
+
+
+
+
+
+
+
+
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21. Sodium -Na
•Na –alkali metal –1s
2
2s
2
2p
6
3s
1
•Two Na atoms come to closes –3s orbital overlaps
•If 3
rd
Na atom comes, valence e
–
occupy 3p state –
(3s & 3p state are closer)
•Na cannot form 2 e
–
pair with other atoms, since Na •Na cannot form 2 e
–
pair with other atoms, since Na
have only 1 e
–
•Structure of Na –BCC : each Na atom form 1/8
th
of e
–
pair bond with each of its neighbours.
•It is possible only if e
–
pair resonates among the 8
pair of Na atom.
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22. Properties of Metallic bonding
•Less directional
•Weaker than ionic and covalent
•Binding energy = 1eV to 5eV
•Low Melting and Boling points•Low Melting and Boling points
•High ductile & malleable
•High thermal and electric conductivity
•High optical reflection and absorption
coefficients.
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23. Van Van dder Waals Bonder Waals Bondiningg
•Van DerWaals bondsoccur between neutral atoms(He, Ne,
Ar, etc)and molecules(O
2 , Cl
2 , CO
2 , CH
4 , etc).
•Dipole interaction between atoms
•Temporary dipoles formed in between adjacent atoms due to
natural fluctuations in the electron density of all molecules.
•Temporary dipoles attract one molecule to another -Van der
Waals' force
•Electric field due to dipole induce dipole moment of
neighbour.
•Dipole –induced dipole interaction –Van derWaals bond
•Dispersion bond
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24. •Theshapeofamoleculeinfluencesitsabilitytoform
temporarydipoles.
•Longthinmoleculescanpackclosertoeachotherthan
moleculesthataremorespherical.
•Thebiggerthe'surfacearea'ofamolecule,thegreaterthe
vanderWaal'sforceswillbe.
Homonuclearmolecules,
such as iodine, develop
temporary dipoles due to
natural fluctuations of electron
density within the molecule
Heteronuclear molecules,
such as H-Cl have permanent
dipoles that attract the opposite
pole in other molecules.
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25. Van der waals interaction occurs generally between
Dipoles formed as the charge centers of one atom displaced
(do not coincides) in the presence of other.
Van der waals interaction occurs generally between
atoms which have noble gas configuration.
van der waals
bonding
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26. Properties of Van derWaals bond-
•Binding energy = 0.1 eV/bond
•Non directional
•Liquifiedat low temperature
•Very weak force (Van derWaal's forces are of the •Very weak force (Van derWaal's forces are of the
order of 1%of the strength of a covalent bond)
•At room temperature, E
thermal> BE -exist in
gaseous state.
•Very low Melting and Boiling point
•Poor conductor of heat and electricity.
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27. Hydrogen BondıngHydrogen Bondıng
•Ahydrogenatom,havingoneelectron,canbecovalentlybondedto
onlyoneatom.However,thehydrogenatomcaninvolveitselfinan
additionalelectrostaticbondwithasecondatomofhighly
electronegativecharactersuchasfluorineoroxygen.Thissecond
bondpermitsahydrogenbondbetweentwoatomsorstrucures.
Hydrogenbondsconnectwater
moleculesinordinaryice.
Hydrogenbondingisalsovery
importantinproteinsand
nucleicacidsandthereforein
lifeprocesses.
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28. •Interaction (not usual bond)
•Intermolecular rather than intramolecular
•A sub-covalent bonding
•Dipole –dipole interaction
Hydrogen BondıngHydrogen Bondıng
•Dipole –dipole interaction
•Strength –1% of covalent bond only -varies
from 0.1 to 0.5 eV/atom
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