Bonding & Structure

K Warne

Bonding & Structure

Objectives: At the end of this unit you should be able to:-

Explain how metallic bonding determines the prosperities of metals

State/explain (understand) the significance of valence electrons

State the conditions for covalent bonding. Explain the properties of substances (simple and

giant covalent) in terms of their bonding and structure.

Know (state) conditions for ionic bonding. Name chemical compounds correctly. List the characteristics of different states of matter.

Bonding

O

H

H

H2O

O

H

H

H2O

O

OH

H

H

H

Bonding takes place when atoms react to form molecules. Example: Two hydrogen molecules and one oxygen molecule react to form two water molecules.

Two hydrogen one oxygen two water Molecules and molecule react to form molecules

Atomic Radius Note the trends in atomic radius across the periodic table.

VALENCY

Valency – ……………….. of electrons ……..….. or ……….... to have a FULL valence level. (Outer shell)

H He

Li Be B C N OF Ne

Valence electrons – those in ……………. shell.

Na Mg Al Si P S Cl Ar

VALENCY

Valency – number of electrons lost or gained to have a FULL valence level. (Outer shell)

H He

Li Be B C N OF Ne

Valence electrons – those in outer shell.

METALS NON - METALS

Covalent bondA shared PAIR of electrons.

Formed between _____________________________. Pure covalent bonds have ____________________ SHARING

of the electrons. _________________ Molecules; H-H, (H2), O2, F2, Cl2, Br2, I2,

N2, Common Ions also covalently bonded

KNOW formulae; eg sulphate ion SO42-

H x H• H H

In covalent substances the electrons are strongly held in the bonds and so the substance will NOT conduct electricity.

Covalent bondA shared PAIR of electrons.

Electrons from one atom are attracted strongly by the nucleus of another atom.

Formed between non metals. (Attract electrons strongly!)

Pure covalent bonds have EQUAL SHARING of the electrons.

In diatomic Molecules; H2, O2, F2, Cl2, Br2, I2, N2,

H H

In covalent substances the electrons are strongly held in the bonds and so the substance will NOT conduct electricity.

HH •x

Covalent bond – Bohr Diagrams (G9)

x

x

x

x O O O

x

x

x

x

xx

xO

x

O

O

H H

H

H

x

x

xx

O x

xxx

xx

O x

x

xx

xx

O x

xxx

xx

O x

x

xx

xx

O xx

xx

xx

Ox

xx

x xx

O O

“Dot Cross Diagrams” - Lewis & Couper Notation

Lewis DiagramsCouper Notation

Chemical Formulae

…………

Name:Oxygen

O x

xxx

xx

O x

x

xx

xx

O x

xxx

xx

O x

x

xx

xx

O xx

xx

xx

Ox

xx

x xx

O=O

“Dot Cross Diagrams” - Lewis & Couper Notation

Lewis DiagramsCouper Notation

Chemical Formulae

O2

Name:Oxygen

Covalent Molecules H2, O2, F2, Cl2, Br2, N2, H2O, NH3, CH4

CO2, NH4+,

CL

Covalent Molecules H2, O2, F2, Cl2, Br2, N2, H2O, NH3, CH4

CO2, NH4+,

Covalent Molecules H2, O2, F2, Cl2, Br2, N2, H2O, NH3, CH4

CO2, NH4+,

Ionic Bonding Formed when there is a …………. of …………………...

Formed between ………….. and ………………….

Metals …………………….. and become ……………………... ions -

CATIONS.

Non metals …………………... and become …………………………. ions - ANIONS.

…………………………… between oppositely charged ions bonds the ions together.

Na.

..

:Cl: -

..

Na+

.:Cl: ..

..

Na. + : Cl: --> [Na]+ [Cl]-

.

ELECTROSTATIC ATTRACTION

Formed when there is a transfer of electrons.

Formed between metals and non metals.

Metals lose electrons and become positively charged ions - CATIONS.

Non metals gain electrons and become negatively charged ions – ANIONS – called CHLORIDE. (“ide” = negative ion)

Electrostatic attraction between oppositely charged ions bonds the ions together.

Na.

..

:Cl: -

..

Na+

.:Cl: ..

..

Na. + : Cl: --> [Na]+ [Cl]-

.

ELECTROSTATIC ATTRACTION

Ionic Bonding

Sodium atomChlorine atom

Sodium ion

Chloride ion

Ionic Bonding – Bohr Diagrams

The final compound is ALWAYS NEUTRAL The total charges of the cations and anions must balance

out.

p=17 n=18

Cl

p=17 n=18

Cl--1

p=11 n=12

Na

p=11 n=12

Na+

+1

Chlorine atom

Chloride ion

Sodium atomSodium ion

Ionisation EnergyThe ENERGY REQUIRED to REMOVE AN ELECTRON completely from an atom in the GAS PHASE.

Sodium atom Sodium ion

Whenever ionic bonding occurs this process must take place.

Gas phase:The atoms are in the gas phase as the energy put in has melted and vapourised them.

ELECTRON AFFINITY

The amount of ENERGY RELEASED when an electron is added to a gaseous atom. This always accompanies the formation of an ionic bond.

e-

Formation of Ionic Bond

1. Write down all the steps that need to take place for this change to take place.

2. Try and place the steps in order.

3. Decide which steps would be endothermic and which would be exothermic.

Na(s) + Cl2(g) NaCl(s)

Formation of Ionic Bond

A large amount of energy (lattice) is released when the gaseous ions bond together into the ionic crystal lattice.

Ionic compounds are therefore very stable and require large amounts of energy to break the bonding.

Ionic compounds have HIGH MELTING POINTS we say they are thermally stable.

Na(s) + 1/2 Cl2(g) NaCl(s)

Na(g) + 1/2 Cl2(g)

Na(g) + Cl(g)

Na+(g) + e- + Cl(g)

Na+(g) + Cl-

(g)

Formation of Ionic Bond

A large amount of energy (lattice) is released when the gaseous ions bond together into the ionic crystal lattice.

Ionic compounds are therefore very stable and require large amounts of energy to break the bonding.

Ionic compounds have HIGH MELTING POINTS we say they are thermally stable.

Na(s) + 1/2 Cl2(g) NaCl(s)

Na(g) + 1/2 Cl2(g)

Na(g) + Cl(g)

Na+(g) + e- + Cl(g)

Na+(g) + Cl-

(g) Ionisation Energy

Dissociation Energy

Sublimation Energy

Electron Affinity

Lattice Energy

MUST BE LEARNT BY HEART!

ONE TWO THREE

Hydrogen H+ Beryllium Be2+ Aluminium Al3+

Lithium Li+ Magnesium Mg2+ Iron(III) Fe3+

Sodium Na+ Calcium Ca2+  

Potassium K+ Barium Ba2+  

Silver Ag+ Lead Pb2+  

Copper(I) Cu+ Zinc Zn2+  

Ammonium NH4+ Iron(II) Fe2+  

Oxonium H3O+ Copper(II) Cu2+  

VALENCY TABLE 1

VALENCY TABLE 2 Negative IonsFluoride F- Oxide O2- Nitride N3-

Chloride Cl- Sulphide S2- Phosphate PO43-

Bromide Br- Carbonate CO32-  

Iodide I- Sulphate SO42-  

Hydroxide OH-    

Nitrate NO3-    

Hydrogencarbonate HCO3-    

Hydrogensulphate HSO4-    

Permanganate MnO4-    

Ethanoate CH3COO-

   

The trivial names for HCO3- and HSO4

- are bicarbonate and bisulphate, respectively.

Bonding - Metallic Bonding- Exists between

_________________.

- Metal electrons are _____________ - therefore they become ______________________ (move from one atom to another).

- This leaves _______________ - which become surrounded by a ‘sea’ of ______________________ electrons.

- A force of _______________________ exists between the delocalized ___________________ and the positive ___________- which forms the ___________________ bond.

All the _____________ of metals can be explained in terms of this bonding.

Bonding - Metallic Bonding

- Exists between metal atoms.

- Metal electrons are weakly held - therefore they become delocalized (move from one atom to another).

- This leaves positive ions - which become surrounded by a ‘sea’ of delocalized electrons.

- A force of electrostatic attraction exists between the delocalized electrons and the positive ions which is the metallic bond.

All the properties of metals can be explained in terms of this bonding.

Explaining Metal PropertiesProperty Explanation

Malleable

Ductile

Conductors of electricity

Shiny (Luster)

Explaining Metal PropertiesProperty Explanation

Malleable

Weakly held electrons are able to move from one atom to another (delocalized). If subjected to significant force the atoms/ions are able to change positions and change the shape of the metal.

DuctileWeakly held electrons are able to move from one atom to another (delocalized). If subjected to significant stretching force the atoms/ions are able to change positions and be drawn into wires.

Conductors of

electricity

Weakly held electrons are able to move from one atom to another (delocalized). If subjected to a potential difference the electrons can drift across the metal and conduct an electric current

Shiny (Luster)

Weakly held electrons are able to move from one atom to another (delocalized). Rough spots on surface can be smoothed over so surface can be polished – also electrons can absorb and radiate light.

Bonding SummaryCovalent

Ionic• • •

Metallic• •

H xH•

Cl-Na+

Properties• • • • •

Properties• • • • •

Properties• • • • • .

H-H

Eg

Bonding SummaryCovalent Non metals Shared

electrons Molecules

Ionic• Metals + non metals • +/- Ions - Lattice• electrostatic attraction

Metallic• Metals• “delocalised”

electrons

H xH•

Cl-Na+

Properties• Non - conducting• (Electrons held in

bond.)• V Low or V High

melting points• Insoluble (H2O)

Properties• High Melting points• Soluble (H2O)• Conduct electricity when

ions free to move(liquid or solution).

Properties• Good Conductors• Malleable• Ductile• Luster (shiny).

H-H

Eg Hydrogen (H2)

Network Solids

From World Book © 2002 World Book, Inc., 233 N. Michigan Avenue, Suite 2000, Chicago, IL 60601. All rights reserved. World Book illustrations by Oxford Illustrators Limited and Bensen Studios

Strong covalent bonds

• Network solids have strong bonds between all atoms.• The structure is extended in three dimensions.• Extensive bonding and a GIANT STRUCTURE ensure the substance has high

boiling and melting points are insoluble

Strong covalent bonds

DiamondGraphite

Delocalised electrons - Weaker van der waals forces between the layers

Network Solids

Diamond

Graphite

Properties:• Strong/ hard/brittle – high m. & bpts.• Electrical insulator (electrons held in

bonds) in all phases – no ions.• insoluble

Phases of Matter

PLASMA+

++

+ +

+

There are FOUR states or phases of matter.

1

2

3

4

Molecular solids

From World Book © 2002 World Book, Inc., 233 N. Michigan Avenue, Suite 2000, Chicago, IL 60601. All rights reserved. World Book diagram by Linda Kinnaman

Ice

Iodine

molecules

Strong covalent bonds

Weaker intermolecular bonds

Water molecule

Metals

(Delocalised electrons)

Strong electromagnetic attraction between ions and ‘sea’ of delocalised electrons.

GIANT structure – extensive strong bonding in 3 dimensions and extended structure

High melting points & boiling points

Ionic Solids – Giant NetworkIonic bonds

An extended lattice (Regular 3D arrangement) of positive and negative ions. Strong bonding throughout ensures the structure has VERY high melting points..

Na+

Cl-

Properties:• Hard/strong/brittle – high melting & boiling points• Electrical insulator (solid – ions can’t move) – conductor in solution or

liquid phase – ions free to move.

Electrical conductivity

anion cation

No free moving charges in the solid state.

The ions are free to move if acted upon by an electric field.

Poslitive electrode

Negative electrode

In metal the delocalised electrons are free to carry an electric current.

Dissolution (dissolving) of an Ionic Solid

Types>> Network Molecular Ionic Metallic

Particles

Bonds

Structure

Properties

Examples

Types>> Network Molecular Ionic Metallic

Particles atoms molecules Ions + and - + Ions and Electrons

Bonds Covalent bonds Inter molecular bonds (weak) Ionic bonds Metallic bonds

Structure(Simple or giant)

GIANT MOLECULE

Simple MOLECULE

GIANT LATTICE

GIANT LATTICE

Properties

Hard/StrongVERY HIGH

melting pointsNon conducting

(usually)

Low mp & BpNon conductors

Weak/BrittleSoluble in Non –

polar solvents

HIGH mp & bpHard strong

crystals /brittleSoluble in polar

solventsConduct in

solution or in liquid form

Malleable, ductile, lustre (shiny), good conductors

Examples C – diamondGraphite

Water/IceIodine

Sulphurchlorine

Salts, sodium chloride, zinc

chloride…

Copper iron etc.

MicroscopyHow do we know about these structures??