What are the four main types of structure used to classify elements and compounds?

Ionic, simple molecular (covalent), giant covalent and metallic.

Which type of structure consists of small separate molecules held together by weak forces between them?

A simple molecular (covalent) structure.

Why do giant covalent substances melt at much higher temperatures than simple molecular substances?

Melting a giant covalent substance breaks strong covalent bonds, while melting a simple molecular substance only overcomes weak forces between molecules.

Edexcel GCSE Chemistry 1CH0

Key Concepts in Chemistry

Topic overview Formulae, word equations and balanced equations Hazard symbols and assessing risk The changing model of the atom Protons, neutrons and electrons The nucleus, mass number and atomic mass Elements and isotopes Calculating particle numbers and relative atomic mass Mendeleev's periodic table How the modern periodic table is arranged Electronic configuration and the periodic table How ionic bonds form Ions in ionic compounds Formulae of ionic compounds and ionic equations Naming compounds and the ionic lattice Covalent bonds and molecules Dot and cross diagrams for simple molecules Classifying substances and the properties of ionic compounds Properties of simple molecular substances, and forms of carbon Graphite and diamond Fullerenes and graphene Polymers and models of bonding The properties of metals Relative formula mass and percentage composition Empirical and molecular formulae Conservation of mass in closed and open systems Reacting masses from balanced equations Concentration in grams per cubic decimetre Moles and the Avogadro constant Limiting reactants and stoichiometry

States of Matter and Mixtures

Topic overview The three states of matter and changes of state Energy changes during changes of state, and predicting state Pure substances and melting point data Choosing a separation technique Separating a mixture in practice Paper chromatography and interpreting a chromatogram Investigating inks by distillation and chromatography Making water potable

Chemical Changes

Topic overview Acids, alkalis and the pH scale Indicators: litmus, methyl orange and phenolphthalein Hydrogen ion concentration and the pH scale Investigating pH change when neutralising an acid Dilute and concentrated, weak and strong acids Bases and alkalis Reactions of acids, and testing for hydrogen and carbon dioxide Neutralisation and its ionic equation Preparing soluble salts from insoluble and soluble reactants Preparing pure, dry copper sulfate crystals Carrying out an acid-alkali titration Solubility rules Predicting precipitates and preparing an insoluble salt Electrolytes and what electrolysis is Movement of ions and predicting the products of molten electrolysis Electrolysis with inert electrodes Writing half equations Oxidation and reduction at the electrodes Electrolysis of copper sulfate solution Investigating the electrolysis of copper sulfate

Extracting Metals and Equilibria

Topic overview Investigating the reactivity of metals Displacement reactions as redox reactions The reactivity series Ores, oxidation and reduction Choosing a method to extract a metal Biological methods of metal extraction Corrosion resistance and recycling metals Life cycle assessment Reversible reactions and dynamic equilibrium The Haber process and its conditions Changing the position of an equilibrium

Transition Metals, Quantitative Chemistry and Industrial Processes

Topic overview Transition metals and their properties Corrosion and electroplating Preventing rusting Alloys and alloy steels How the uses of metals relate to their properties Concentration in mol dm-3 and titration calculations Carrying out an accurate titration Percentage yield Atom economy and choosing a reaction pathway Molar volume of a gas Avogadro's law and gas volumes The Haber process Conditions used in industrial reactions Fertilisers and ammonium salts Preparing ammonium sulfate in the lab and in industry Chemical cells and fuel cells Evaluating fuel cells

Groups in the Periodic Table

Topic overview The groups of the periodic table, and the alkali metals Reactions of the alkali metals with water The pattern in alkali metal reactivity and why it happens Physical properties of the halogens The test for chlorine, and halogens reacting with metals Hydrogen halides, and explaining halogen reactivity Displacement reactions of the halogens Group 0: the noble gases

Rates of Reaction and Energy Changes

Topic overview Investigating the rate of a reaction Measuring rate and interpreting rate graphs Collision theory and factors affecting rate Catalysts and enzymes Exothermic and endothermic changes Bond breaking, bond making and the overall energy change Bond energies, activation energy and reaction profiles

Fuels and Earth Science

Topic overview Hydrocarbons and crude oil Fractional distillation and the fractions Properties of the fractions and homologous series Complete and incomplete combustion Carbon monoxide and soot Pollutants and acid rain Hydrogen and fossil fuels compared Cracking and why it is necessary The Earth's early atmosphere How the oceans formed and how oxygen appeared The test for oxygen and the greenhouse gases Today's atmosphere and evidence for climate change

Chemical Analysis, Organic Chemistry and Materials

Topic overview Why an ion test must be unique, and flame tests Tests for metal ions and for ammonia Tests for carbonate, sulfate and halide ions Identifying the ions in an unknown salt Instrumental methods and flame photometry Alkanes and why they are saturated Alkenes and why they are unsaturated Reactions of alkenes, and combustion What a polymer is, and how poly(ethene) forms Other addition polymers, and monomers from polymers Uses of polymers, and natural polymers including DNA Polyesters and condensation polymerisation Problems with polymers and recycling Alcohols and the -OH functional group Comparing the energy released by alcohol fuels Making ethanol by fermentation and distillation Carboxylic acids and the -COOH functional group Oxidising alcohols to carboxylic acids, and homologous series The size of nanoparticles Uses and risks of nanoparticles Choosing a material for a use

Key Concepts in Chemistry

Classifying substances and the properties of ionic compounds

1 thing to know
Papers 1 and 2

Overview

The four structure types, telling them apart by melting point, conductivity and solubility, and why ionic compounds melt high and conduct only when molten or dissolved.

What you need to know

Answer each one before you reveal it.

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Key term

Explain why ionic compounds have high melting points but conduct when melted or dissolved, and why magnesium oxide melts higher than sodium chloride.

Questions from this subtopic

Each one with the model answer underneath.

1
What are the four main types of structure used to classify elements and compounds?
Model answer
Ionic, simple molecular (covalent), giant covalent and metallic.
2
Which type of structure is built from a lattice of positive and negative ions?
Model answer
An ionic structure.
3
Which type of structure consists of small separate molecules held together by weak forces between them?
Model answer
A simple molecular (covalent) structure.
4
Which type of structure is a lattice of positive ions surrounded by delocalised electrons?
Model answer
A metallic structure.
5
Why do giant covalent substances melt at much higher temperatures than simple molecular substances?
Model answer
Melting a giant covalent substance breaks strong covalent bonds, while melting a simple molecular substance only overcomes weak forces between molecules.
6
A solid does not conduct electricity, but its solution in water does. What type of structure does it have?
Model answer
An ionic structure.

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Key Concepts in Chemistry

States of Matter and Mixtures

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Extracting Metals and Equilibria

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Classifying substances and the properties of ionic compounds

Overview

What you need to know

Explain why ionic compounds have high melting points but conduct when melted or dissolved, and why magnesium oxide melts higher than sodium chloride.

Questions from this subtopic

What are the four main types of structure used to classify elements and compounds?

Which type of structure is built from a lattice of positive and negative ions?

Which type of structure consists of small separate molecules held together by weak forces between them?

Which type of structure is a lattice of positive ions surrounded by delocalised electrons?

Why do giant covalent substances melt at much higher temperatures than simple molecular substances?

A solid does not conduct electricity, but its solution in water does. What type of structure does it have?

Other ways to work this

What is inside Levo

See a huge jump in your memorisation

Cram a whole paper in one sitting

Blank Blitz consolidates the facts

Build It trains answer structure

Test It catches misconceptions

Brain Breaks between sessions

Every question in Key Concepts in Chemistry, on a schedule.