# Grade 9 - Unit 3 - Periodic Table, Formulae and Equations

In this unit, students will study the patterns that occur in the Periodic Table and use them to help predict the behaviour of elements and the properties of the compounds that they form. They will use their knowledge of atomic structure to deduce the formulae of chemical substances. Students will also gain experience of writing balanced chemical equations for simple chemical reactions. The theory will be illustrated by a series of practical activities.

## Learning targets

#### SMEO

Careful observation and recognition of patterns of behavior allows us to make predictions about the behavior of the natural world

### C4. Stoichiometry

• Use the symbols of the elements to write the formulae of simple compounds
• Deduce the formula of a simple compound from the relative numbers of atoms present
• Deduce the formula of a simple compound from a model or a diagrammatic representation
• Construct and use word equations
• Supplement: Determine the formula of an ionic compound from the charges on the ions present
• Supplement: Construct and use symbolic equations with state symbols
• Supplement: Deduce the balanced equation for a chemical reaction, given relevant information.

### C9. The Periodic Table

• Describe the way the Periodic Table classifies elements in order of proton number
• Supplement: Use the Periodic Table to predict properties of elements by means of groups and periods

#### C9.1 Periodic trends

• Describe the change from metallic to nonmetallic character across a period
• Supplement: Describe the relationship between Group number, number of outer-shell (valency) electrons and metallic/non-metallic character

#### C9.2 Group properties

• Describe lithium, sodium and potassium in Group I as a collection of relatively soft metals showing a trend in melting point and reaction with water
• Describe the trends in properties of chlorine, bromine and iodine in Group VII including colour, physical state and reactions with other halide ions
• Supplement: Predict the properties of other elements in Group I, given data where appropriate
• Supplement: Predict the properties of other elements in Group VII, given data where appropriate

#### C9.3 Transition elements

• Describe the transition elements as a collection of metals having high densities, high melting points and forming coloured compounds, and which, as elements and compounds, often act as catalysts.

#### C9.4 Noble gases

• Describe the noble gases as being unreactive
• Supplement: Describe the uses of the noble gases in providing an inert atmosphere, i.e. argon in lamps, helium for filling balloons.