Why do elements in the same group of the Periodic Table react in similar ways?

They have the same number of electrons in their outer shell, so they form ions of the same charge and behave alike chemically.

Caesium lies at the bottom of Group 1. Predict what happens when it is added to cold water.

It reacts explosively, forming caesium hydroxide solution and hydrogen gas.

Calcium is in Group 2. Predict the formula of the compound it forms with chlorine.

CaCl₂, because a calcium atom loses two electrons and each chlorine atom gains one.

Predict what is seen when chlorine solution is added to colourless sodium iodide solution.

The solution turns brown as iodine is displaced, because chlorine is more reactive than iodine.

OCR GCSE Chemistry A J248

Chemical Reactions

Topic overview Writing formulae of elements and compounds Balanced equations, and deducing formulae from ions Ionic equations, and state symbols The mole and the Avogadro constant Conservation of mass, and changes of mass in open systems Stoichiometry, and calculating reacting masses Exothermic and endothermic reactions, and reaction profiles Activation energy, and bond energy calculations Oxidation and reduction, by oxygen and by electrons Acids, alkalis and neutralisation The ionic equation for neutralisation, and reactions of acids Dilute and concentrated, weak and strong The pH scale, and hydrogen ion concentration pH as a factor of ten, and measuring pH 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 Nanoparticles: size and surface area to volume Uses and risks of nanoparticulate materials

Global Challenges

Topic overview Extracting metals by reduction and by electrolysis Biological methods of metal extraction Rate against yield in industry, and reaction conditions The Haber process and fertiliser production Nitrogen, phosphorus and potassium in agriculture Life cycle assessment Recycling, and the decisions behind it Alloys, and the corrosion of metals Comparing glass, ceramics, polymers, composites and metals Functional groups and homologous series Predicting the products of organic reactions Addition polymerisation Condensation polymerisation, and making a polymer DNA and other natural polymers Fractional distillation of crude oil The fractions, and crude oil as a feedstock Dependence on hydrocarbons, and cracking Chemical cells and fuel cells 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 Concentration in mol/dm³, and titration Titration calculations, and the mass of a solute Molar gas volume and the volumes of gases Theoretical mass and percentage yield Atom economy, and choosing a reaction pathway 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 Changing the conditions of an equilibrium Activation energy, and enzymes as catalysts

Particles

Topic overview The particle model and changes of state Limitations of the particle model 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 Transition metals Predicting reactivity from the Periodic Table Reactivity of metals with water and acids Tests for oxygen, hydrogen, carbon dioxide and chlorine Tests for aqueous cations and anions Flame tests, and identifying metal ions Identifying a species from test results Instrumental methods of analysis

Predicting and Identifying Reactions

Predicting reactivity from the Periodic Table

3 things to know
Paper 4

Overview

Where metals and non-metals sit, why a group reacts alike, caesium in water, the formulae of potassium iodide and calcium chloride, chlorine displacing iodine, why argon does not react, and recognising a Group 1 metal.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Predict the formulae of potassium iodide and calcium chloride, and what is seen when chlorine solution is added to sodium iodide solution.

Key term

Where are the metals and the non-metals found in the Periodic Table?

Key term

Predict the formula of the compound formed between potassium and iodine.

Questions from this subtopic

Each one with the model answer underneath.

1
Where are the metals and the non-metals found in the Periodic Table?
Model answer
Metals are on the left and in the centre, and non-metals are on the right-hand side.
2
Why do elements in the same group of the Periodic Table react in similar ways?
Model answer
They have the same number of electrons in their outer shell, so they form ions of the same charge and behave alike chemically.
3
Caesium lies at the bottom of Group 1. Predict what happens when it is added to cold water.
Model answer
It reacts explosively, forming caesium hydroxide solution and hydrogen gas.
4
Predict the formula of the compound formed between potassium and iodine.
Model answer
KI, because potassium loses one electron and iodine gains one.
5
Calcium is in Group 2. Predict the formula of the compound it forms with chlorine.
Model answer
CaCl₂, because a calcium atom loses two electrons and each chlorine atom gains one.
6
Predict what is seen when chlorine solution is added to colourless sodium iodide solution.
Model answer
The solution turns brown as iodine is displaced, because chlorine is more reactive than iodine.

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Chemical Reactions

Elements, Compounds and Mixtures

Global Challenges

Monitoring and Controlling Chemical Reactions

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