ks4 comparing bonding (boardworks)

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KS4 Chemistry

Comparing Bonding


Comparing bonding

Conductivity

Other properties

Melting and boiling point

Summary activities

Bonding and structure

Contents


Types of bonding

There are three ways in which atoms can chemically bond.In each case, electrons are involved in different ways.

ionic bonding – electrons are transferred from metal to non-metal atoms to form positive and negative ions. These oppositely-charged ions are attracted to each other.

covalent bonding – electrons are shared betweennon-metal atoms.

metallic bonding – electrons become delocalized and form a sea of free electrons, which attracts positive metal ions.


Predicting bonding


Bonding Type of structure

Particles in structure

State at room temperature

Ionic

Covalent

Metallic

Bonding and structures

The type of bonding in a substance affects the structure of that substance.

giant ionic millions of ions solidlattice

simple few atoms usually liquid ormolecular solid

giant covalent millions of solidlattice atoms

giant metallic millions of ions solid (exceptlattice mercury – liquid)


Bonding and properties

The bonding and structure of a substance affects the properties of that substance.

Different bonds involve electrons in different ways – this affects properties such as conductivity of electricity and heat.

Different bonds require different amounts of energy to be broken – this affects properties such as melting and boiling point, solubility and hardness.


How do properties differ?

How do the properties of substances differ according to the type of bonding they contain?


Comparing bonding

Conductivity

Other properties


Summary activities


Contents


Melting and boiling point: giant structures

Substances with giant structures generally have high melting and boiling points because all the atoms are strongly bonded together to form a continuous 3D lattice. A large amount of energy is needed to break these bonds.

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strong ionic bonds holds ions together

strong covalent bonds holds atoms together

strong metallic bonds holds ionstogether


Melting and boiling point: molecules

Simple molecular substances have low melting and boiling points because the forces that hold the molecules together are weak and easily broken.

weak bonds between moleculesstrong bonds

within molecules

In general, the larger the molecule, the higher the melting and boiling point.


Comparing bonding

Conductivity

Other properties


Summary activities


Contents


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When liquid (molten) or dissolved, however, the ions are able to break free of the lattice.

Ionic substances cannot conduct electricity when solid because the ions are bonded together in the lattice.

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ions cannot move to carry a charge

ions are able to move and carry a charge

Conductivity – ionic substances


Substances with covalent bonding do not conduct electricity because all the outer electrons are fixed in shells.

The exception is graphite, which has free electrons between layers of carbon atoms.

electrons unable to move and carry a charge

Conductivity – covalent substances


Metals can conduct electricity because the sea of delocalized electrons between the metal ions are free to move anywhere in the structure.

metal ions electrons free to

move and carry an electrical charge

sea of electrons

Conductivity – metals


Bonding and electrical conductivity


Comparing bonding

Conductivity

Other properties


Summary activities


Contents


Substances with giant covalent or metallic structures generally do not dissolve easily in water or other solvents.

This is because dissolving involves breaking bonds, which needs lots of energy.

Many ionic substances dissolve in water because water molecules have a slight electrical charge and can attract the ions away from the lattice.

Simple molecular substances are usually insoluble in water but soluble in solvents such as petrol.

Solubility


Strength

Substances with giant structures are generally hard because a large amount of energy is needed to break ionic, covalent and metallic bonds.

Covalent substances are hard but brittle – the covalent bonds do not bend but break when enough force is applied.

Ionic substances are hard but brittle – when a force is applied, ions with like-charges are brought together. These repulse each other and cause the lattice to shatter.

Metals are hard but malleable and ductile – the delocalized electrons allow the metallic bonds to move.

Graphite is slippery because the weak forces between layers of carbon atoms can easily be broken.


The density of a substance depends on the type and strength of bonding and how the atoms/ions are arranged.

Giant substances, especially metals, are dense because the atoms/ions are tightly packed together.

Substances with simple molecular structures have lower densities. The weak forces between molecules cannot pull the molecules together tightly.

strong bonds cause tight packing

weak bonds cause loose packing

Density


True or false?


Effect of structure on properties


Comparing bonding

Conductivity

Other properties


Summary activities


Contents


Glossary

covalent bond – A strong bond between two atoms in which each atom shares one or more electrons with the other.

delocalized – Electrons that are free to move throughout a structure. In metals, they form a ‘sea of electrons’.

ionic bond – The strong electrostatic force of attraction between oppositely charged ions.

giant structure – A structure containing millions of atoms or ions bonded together. The structure extends in three

dimensions until all available atoms or ions are used up.

lattice – A 3D structure of closely packed atoms or ions.

metallic bonding – The strong attraction between positive metal ions and a sea of electrons.

molecule – A simple structure containing two or more atoms covalently bonded together.


Anagrams


The effect of bonding on properties


Comparing bonding – team game


Multiple-choice quiz

ks4 comparing bonding (boardworks)

Technology

boardworks lt

bonding conductivity

type of bonding

types of bonding

predicting bonding

covalent bonding electrons

metallic bonding electrons

ionic bonding electrons