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Lecture materials for the Introductory Chemistry course for Forensic Scientists, University of Lincoln, UK. See http://forensicchemistry.lincoln.ac.uk/ for more details.
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Chemical Bonding 4 IONIC, METALLIC & COORDINATE BONDS
University of Lincoln presentation
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Ionic Bonding
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IONIC BONDING
• Very important form of bonding – main bonding mechanism of metals:
• >80 elements are METALS• 19 elements are non-metals• 5 elements are metalloids
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Ionic Bonding – main bonding mechanism of the metals
Ionic
f - block elements
H
BeLi
Na
K
Rb
Cs
Fr
Mg
Ca
Sr
Ba
Ra
Sc
Y
La
Ac
Ti V Cr Mn Fe Co Ni Cu Zn
Zr
Hf Ta W Re Os Ir Pt Au Hg Tl
Nb Mo Tc Ru Rh Pd Ag Cd In Sn
Pb Bi Po At Rn
Xe
Kr
Ar
Ne
Sb Te I
Ga
Al
Ge
Si P S Cl
As Se Br
Ce Pr Nd Pm Sm
Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
He
B C N O F
LanthanoidsActinoids
d – block elements
Hydrogen and s – block elements
p – block elements
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Forming Ionic Bonds• IONIC BONDS are electrostatic in
nature, and are formed by transferring electrons from an electron giver to an electron taker
ELECTRON GIVER ELECTRON TAKERe–
Cation (+) Anion (-)
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Electron Givers
• Most metals have 1–3 valence electrons that they would like to lose
• Metals are therefore ELECTRON GIVERS
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Electron Takers
• Elements on the RHS of the periodic table (non-metals) would like to gain electrons
• Non-metals are therefore good ELECTRON TAKERS
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For Example…
Cu(I) Cu – e– Cu+
Cu(II) Cu – 2e– Cu2+
O + 2e– O2–
Overall reactions:
Cu(I) 4Cu + O2 2Cu2O
Cu(II) 2Cu + O2 2CuO
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Some Common Ions
ANIONS
Symbol NameCl– Chloride
O2– Oxide
O22– Peroxide
S2– Sulphide
CO32– Carbonate
SO42– Sulphate
OH– Hydroxide
SiO44– Silicate
CATIONS
Symbol NameNa+ Sodium
K+ Potassium
Ca2+ Calcium
Cu+ Copper(I)
Cu2+ Copper(II)
Fe2+ Iron(II)
Fe3+ Iron(III)
Sn2+ Tin(II)
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Structural types
• Common geometries adopted:
Octahedral geometryTetrahedral geometry
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• There are only a few structural shapes adopted in solid ionic compounds (salts):
•Rock Salt (sodium chloride) •Caesium chloride •Fluorite (calcium fluoride)•Rutile (titanium(IV) oxide)
Structural shapes
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Rock Salt StructureCompound Formula Cation Anion
Sodium chloride NaCl Na+ Cl–
Sodium fluoride NaF Na+ F–
Sodium hydride NaH Na+ H–
Lithium chloride LiCl Li+ Cl–
Potassium bromide KBr K+ Br–
Potassium iodide KI K+ I–
Silver fluoride AgF Ag+ F–
Silver chloride AgCl Ag+ Cl–
Magnesium oxide MgO Mg2+ O2–
Calcium oxide CaO Ca2+ O2–
Barium oxide BaO Ba2+ O2–
Iron(II) oxide FeO Fe2+ O2–
Magnesium sulfide MgS Mg2+ S2–
Lead(II) sulfide PbS Pb2+ S2–
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Rock Salt Type – cubic
Cation+
Anion–
The COORDINATION NUMBER of each Cation+ ion = 6
The COORDINATION NUMBER of each Anion– ion = 6
NaCl: 801 CS=35.9g/100ml(25C)
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The COORDINATION NUMBER of an ion is the number of nearest neighbours
Definition…
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Caesium Chloride Type – BCC
BCC = Body centred cubic
Cesium chloride unit cell (space filling diagram)
Cesium chloride unit cell (ball and stick diagram)
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Caesium Chloride Type – BCC
Cation+
Anion–
The COORDINATION NUMBER of each Cation+ ion = 8
The COORDINATION NUMBER of each Anion– ion = 8
CsCl: 645 CS=162g/100ml(1 C)
A unit cell of caesium chloride Extending the caesium chloride structure
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Fluorite Type
Cation+
Anion–
The COORDINATION NUMBER of each Cation+ ion = 8
The COORDINATION NUMBER of each Anion– ion = 4
CaF2: 1402 CS=virtually insoluble
CaF2 unit cell
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Rutile Type
Cation+
Anion–
The COORDINATION NUMBER of each Cation+ ion = 6
The COORDINATION NUMBER of each Anion– ion = 3
TiO2: 1870 CS=Insoluble
Unit cell of rutile type TiO2
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Metallic Bonding
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Solid State Metals
• METALLIC BONDING is a variation on both covalent and ionic bonding:
•The bonding is electrostatic in nature (like ionic)
•but involves the sharing of electrons (like covalent) over many atoms of the same type
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The Metallic Bond
Metal ion
Electron
The structure of a metal consists of a lattice of bonded metal cations with a ‘sea of electrons’. The electrons are not bound, and can move throughout the structure
– hence metals are good conductors of electricity
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Coordinate Bonding
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Transition Metals
The TRANSITION METALS (d- and f-block metals) usually form COORDINATE BONDS
f - block elements
H
BeLi
Na
K
Rb
Cs
Fr
Mg
Ca
Sr
Ba
Ra
Sc
Y
La
Ac
Ti V Cr Mn Fe Co Ni Cu Zn
Zr
Hf Ta W Re Os Ir Pt Au Hg Tl
Nb Mo Tc Ru Rh Pd Ag Cd In Sn
Pb Bi Po At Rn
Xe
Kr
Ar
Ne
Sb Te I
Ga
Al
Ge
Si P S Cl
As Se Br
Ce Pr Nd Pm Sm
Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
He
B C N O F
LanthanoidsActinoids
d – block elements
Hydrogen and s – block elements
p – block elements
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The Coordinate Bond
• The COORDINATE BOND occurs when a species donates its lone pair of electrons to a metal ion
Cl Lone
pair
The metal does NOT use
its own valence
electrons for bonding
Fe2
+
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Definition…
• A species that donates a lone pair of electrons to a metal ion to form a coordinate bond is called a LIGAND
• A ligand can be either anionic or neutral
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Definitions…
o Covalent bondo Ionic bondo Metallic bondo Coordinate bondo Coordination numbero Ligand
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Acknowledgements
• JISC• HEA• Centre for Educational Research and
Development• School of natural and applied sciences• School of Journalism• SirenFM• http://tango.freedesktop.org
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