Identifying an Ionic Compound. Objectives: To learn and test for metal ions and non-metal ions and then apply them to discover the identity of an unknown ionically bonded substance

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Identifying an Ionic Compound-


        Ionic compounds are defined as being compounds where two or more ions (an atom or group of atoms with an overall electrical charge) are held next to each other by electrical attraction. One of the ions has a positive charge - called a “cation”, and the other has a negative charge - called “anion”.  Cations are usually metal atoms and anions are either nonmetal or polyatomic ions (ions with more than one atom).

        Usually, when we have ionic compounds, they form large crystals that you can see with the naked eye. Table salt is one of this- if you look at a crystal of salt, you can see that it has in irregular cube shape. This is because salt likes to stack in little cube-shaped blocks. When forming salt, Na readily loses an electron and Cl readily gains an electrons so both can become stable. Heat is added in the reaction so Na burns brightly in CL gas and a white solid forms on the sides of the container. This solid is salt, or sodium chloride. When the chlorine atom gained an electron, the atoms arrange themselves in a lattice. The force of attraction between a cation and anion is a very strong bond called an “ionic bond”. This is an electrostatic attraction. An ionic bond happens between a metal and a nonmetal.

Properties of salts:

  • All ionic compounds form crystals.
  • Ionic compounds tend to have high melting and boiling points due to very strong bonds in the lattice and it takes a lot of energy for these bonds to break.
  • Ionic compounds are very hard and brittle
  • Ionic compounds conduct electricity when they dissolve in water because there are freely moving particles.
  • Ionic compounds are soluble in water. Charges on ionic compounds (dipole-dipole interactions) attract water molecules.

Metals form cations, electron loss forms cations.

Group 1= 1 electron in the outershell (Li+1)

Group II= 2 electrons in the outershell (Be+2)

Group III= 3 electrons in the outershell (Al+3)

Nonmetals form anions, electron gain forms anions.

Group V= 5 electrons in the outershell, so needs to gain 3 electrons. (N-3)

Group VI= 6 electrons in the outershell, so needs to gain 2 electrons. (O-2)

Group VII= 7 electrons in the outershell, so needs to gain 1 electron. (Cl-1)

Ionization energy is the ease of cation formation, but this decreases down a group- so the top part of the group is more reactive.

Electron affinity is the ease of anion formation.

To form an ionic compound: the compound must be neutral.

  1. Write the chemical symbol for each element and deduce the charge of the two ions. The cation is the first part, the anion is the second part.
  2. Deduce how many of each are required in order for that sum of charges to equal zero.
  3. Numbers of each ions give the subscripts in chemical formulas.
  4. The symbol for the metal is first, followed by the symbol for the nonmetal (each with subscripts).

When naming ionic bonds, the first parts is the name of the metal, the second is the name of the non-metal and the suffix “ide”.


To learn and test for metal ions and non-metal ions and then apply them to discover the identity of an unknown ionically bonded substance

To practice writing the formula for the unknown ionically bonded substance

To develop our observational skills

To become familiar with the chemical solutions as well as the Bunsen Burner

To become familiar with writing your own procedure for the lab, as well as to keep a record of all the materials used.

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To analyze your findings and evaluate your methods.

To reflect on how your experiment could be improved in the future.


x1 Test Tube Rack

x5 Empty Test Tubes

x1 Bunsen Burner

x1 Test Tube Holder

x1 Eye Protection

x1 Test Tube with unknown Solution

x1 Beaker with HCL

x1 Spatula


Part 1:

If I am testing for halide ions using 2cm3 ±0.05 of AgNO3, then a colorful precipitate is going to form but no bubbles will be present.

If I am testing for sulphate ions (SO42) using 2cm3 ±0.05 of 0.1 mol/dm3 HCL ...

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This is a very complex GCSE experiment, using aspects of chemistry that would not usually be encountered until AS level. It is very detailed, uses excellent results tables and makes valid, repeatable conclusions. Overall, this piece of work is 5*