28 Writing formulae for ionic compounds 14-16 Working in groupsSelf assessmentPeer assessmentSharing objectives and criteriaQuestioningUsing feedbackUsing tests

In this activity, ion formulae cards help students check, consolidate and demonstrate their ability to write correct formulae for ionic compounds. Students work cooperatively to demonstrate their mastery of the ideas to each other and the teacher. Following teacher validation of one group, the students themselves then progressively validate other groups.

Learning objectives

Students will be able to:

  • recall the names and formulae of common cations and anions
  • write formulae of ionic compounds.

Sequence of activities

Give each student a set of traffic light cards.

Ask them to indicate whether they know the names of the ions Na+, Fe2+, NO3-, SO42-, S2-.

  • Green if they think that they know
  • Red if they do not know
  • Yellow if they are unsure

Explain that they are going to:

  • work in groups
  • check and demonstrate that they can associate the names and formulae of common ions
  • show that they can use the formulae of ions to construct formulae of ionic compounds.
Give each student a mini whiteboard and an Ion formulae sheet.

Ask them to:

  • write, on the whiteboard, the formulae of sodium bromide, potassium nitrate, calcium sulfate and sodium hydrogencarbonate
  • turn the board over.
Organise students:
  • into groups of four
  • to complete their Ion formulae sheets by writing the names of ions in appropriate places.

When one group believes it has completed this task successfully, check their work. If successful, designate them an Expert Group. Authorise these group members to check the work of other groups.

Allow the checking to cascade.

Give successful groups one set of Ion formula cards and a Formulae for ionic compounds sheet for each student.

Ask them to:

  • arrange the cards to form the formulae of the ionic compounds on their sheet
  • devise and ask questions of each other so that they can demonstrate that they can write down the formulae of ionic compounds (this could be in pairs).

When one group believes it is competent, check their work using random questions. If five questions are correctly answered, designate them an Expert Group. Authorise these group members to check the work of other groups and to designate them as an Expert Group.

Allow the checking to cascade.

With the whole class, ask students to:
  • write on their whiteboards, the formulae of sodium bromide, potassium nitrate, calcium sulfate and sodium hydrogencarbonate
  • compare this with what they wrote at the beginning of the session
  • write in an evaluation of their progress on the Formulae for ionic compounds sheet.

Assessment for learning commentary

The traffic light cards activity gives the learning objectives a personal relevance for the students.

In the two main activities, the focus is on the whole group rather than individuals. For the whole group to succeed, students will support and assess each other.

The element of personal evaluation, using the mini whiteboards at the start and end, promotes student confidence that they can improve.

Resources

Props

For each student

Download Word Download PDF Ion formulae sheet
Download Word Download PDF Formulae for ionic compounds sheet
  • Set of traffic light cards
  • Mini whiteboard

For each group of students

Download Word Download PDF Set of Ion formula cards

Answers

Formulae for ionic compounds:

Compound Formula Compound Formula
Sodium carbonate Na2CO3 Zinc nitrate Zn(NO3)2
Silver nitrate AgNO3 Potassium sulfate K2SO4
Calcium bromide CaBr2 Magnesium sulfide MgS
Copper hydroxide Cu(OH)2 Aluminium hydroxide Al(OH)3
Iron(II) nitrate Fe(NO3)2 Ammonium chloride AlCl3
Iron(III) iodide FeI3 Sodium hydrogen carbonate NaHCO3
Lead sulfate PbSO4 Iron(III) carbonate Fe2(CO3)3