Describe the arrangement of atoms in a giant covalent structure.

A very large number of atoms are all joined by strong covalent bonds in a lattice that continues throughout the whole structure.

Describe the structure of a polymer.

It is made of very large molecules in which many small units are joined by covalent bonds into long chains.

Describe the bonding and arrangement of particles in a metal.

Positive metal ions are packed in regular layers within a sea of delocalised electrons that are free to move.

Which types of substance contain covalent bonds?

Simple molecular substances, giant covalent structures and polymers all contain covalent bonds.

OCR GCSE Combined Science Chemistry J250

Chemical Reactions

Topic overview Writing formulae of elements and compounds Balanced equations, and deducing formulae from ions State symbols in equations Conservation of mass, and changes of mass in open systems Exothermic and endothermic reactions, and reaction profiles Activation energy and why reactions need it Oxidation and reduction in terms of oxygen Acids, alkalis and neutralisation The ionic equation for neutralisation, and reactions of acids The pH scale, acidity and alkalinity Measuring pH with indicators and pH meters Products at the electrodes, and molten ionic compounds Electrolysis of aqueous solutions Inert and non-inert electrodes

Elements, Compounds and Mixtures

Topic overview Purity, and melting point data Relative formula mass and empirical formulae Formulations, and separating mixtures Paper and thin layer chromatography Interpreting chromatograms and Rf values Choosing a purification method Metals and non-metals in the Periodic Table Electron arrangement and position in the Periodic Table Ionic, covalent and metallic bonding compared Dot and cross diagrams, and the limits of models Reactions, electron arrangement and Mendeleev's table Carbon's four bonds, and the variety of organic compounds Diamond, graphite, fullerenes and graphene Bond strength, intermolecular forces and predicting state Bulk properties of ionic, molecular and giant structures

Global Challenges

Topic overview Extracting metals by reduction and by electrolysis Life cycle assessment Recycling, and the decisions behind it Fractional distillation of crude oil The fractions, and crude oil as a feedstock Dependence on hydrocarbons, and cracking The Earth's early atmosphere, and how oxygen developed The greenhouse effect, and evidence for climate change Effects of carbon dioxide and methane, and air pollutants Producing potable water

Monitoring and Controlling Chemical Reactions

Topic overview Measuring the rate of a reaction, and rate graphs Factors affecting rate, and collision theory Surface area and rate Catalysts and how they work Reversible reactions and dynamic equilibrium Activation energy, and enzymes as catalysts

Particles

Topic overview The particle model and changes of state How the atomic model changed, and the structure of the atom The size of atoms, and the subatomic particles Calculating protons, neutrons and electrons

Predicting and Identifying Reactions

Topic overview Groups 1, 7 and 0, and why they behave as they do Predicting reactivity from the Periodic Table Reactivity of metals with water and acids Tests for oxygen, hydrogen, carbon dioxide and chlorine

Elements, Compounds and Mixtures

Ionic, covalent and metallic bonding compared

3 things to know
Paper 3 (Chemistry)

Overview

The bonding and arrangement of particles in ionic compounds, simple molecules, giant covalent structures, polymers and metals, which kinds of atom each type of bonding joins, electron transfer and sharing, the electrostatic attractions that hold ionic, covalent and metallic bonds together, the ions in sodium chloride and magnesium oxide, and why atoms bond at all.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What holds the particles together in ionic, covalent and metallic bonding, and what electron transfer happens when sodium reacts with chlorine?

Key term

Describe the bonding and the arrangement of particles in an ionic compound.

Key term

Describe the bonding in a simple molecular substance.

Questions from this subtopic

Each one with the model answer underneath.

1
Describe the bonding and the arrangement of particles in an ionic compound.
Model answer
Oppositely charged ions are held by strong electrostatic attraction in a giant regular lattice that repeats in all directions.
2
Describe the bonding in a simple molecular substance.
Model answer
Strong covalent bonds hold the atoms together within each small molecule, and only weak intermolecular forces act between the molecules.
3
Describe the arrangement of atoms in a giant covalent structure.
Model answer
A very large number of atoms are all joined by strong covalent bonds in a lattice that continues throughout the whole structure.
4
Describe the structure of a polymer.
Model answer
It is made of very large molecules in which many small units are joined by covalent bonds into long chains.
5
Describe the bonding and arrangement of particles in a metal.
Model answer
Positive metal ions are packed in regular layers within a sea of delocalised electrons that are free to move.
6
Which types of substance contain covalent bonds?
Model answer
Simple molecular substances, giant covalent structures and polymers all contain covalent bonds.

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Chemical Reactions

Elements, Compounds and Mixtures

Global Challenges

Monitoring and Controlling Chemical Reactions

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Values 7.

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AMetals are on the left and in the centre, and non-metals are on the right-hand side.

BKI, because potassium loses one electron and iodine gains one.

CCaCl₂, because a calcium atom loses two electrons and each chlorine atom gains one.

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Sodium ions give a bright yellow flame colour.

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