Chemical Structure: Chemical Bonding. Ionic, Metallic & Coordinate Bonds

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Chemical Bonding 4 IONIC, METALLIC & COORDINATE BONDS

University of Lincoln presentation

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Ionic Bonding



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



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



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 (-)



Electron Givers

• Most metals have 1–3 valence electrons that they would like to lose

• Metals are therefore ELECTRON GIVERS



Electron Takers

• Elements on the RHS of the periodic table (non-metals) would like to gain electrons

• Non-metals are therefore good ELECTRON TAKERS



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



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)



Structural types

• Common geometries adopted:

Octahedral geometryTetrahedral geometry



• 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



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–



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)



The COORDINATION NUMBER of an ion is the number of nearest neighbours

Definition…



Caesium Chloride Type – BCC

BCC = Body centred cubic

Cesium chloride unit cell (space filling diagram)

Cesium chloride unit cell (ball and stick diagram)



Caesium Chloride Type – BCC

Cation+

Anion–



CsCl: 645 CS=162g/100ml(1 C)

A unit cell of caesium chloride Extending the caesium chloride structure



Fluorite Type

Cation+

Anion–



CaF2: 1402 CS=virtually insoluble

CaF2 unit cell



Rutile Type

Cation+

Anion–



TiO2: 1870 CS=Insoluble

Unit cell of rutile type TiO2



Metallic Bonding



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



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



Coordinate Bonding



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



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

+



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



Definitions…

o Covalent bondo Ionic bondo Metallic bondo Coordinate bondo Coordination numbero Ligand



Acknowledgements

• JISC• HEA• Centre for Educational Research and

Development• School of natural and applied sciences• School of Journalism• SirenFM• http://tango.freedesktop.org

http://www.jisc.ac.uk/

http://www.heacademy.ac.uk/