Testing for ions and gases
Chemists are often asked to test a sample of a substance to find out if it contains specific Electrically charged particle, formed when an atom or molecule gains or loses an electron/electrons. or A substance formed by the chemical union of two or more elements.. There are a variety of techniques used to do this.
Testing for ions – flame tests
It is possible to use a flame test to detect the presence of an alkali metal ion.
A cleaned, moistened flame test wire is dipped into a solid sample of the compound. It is then put into the edge of a blue Bunsen flame. The flame colour produced indicates which metal ion is present in the compound.
Flame colours and the metal ion they represent
| Flame colour | Ion present |
| Red | Lithium, Li+ |
| Yellow-orange | Sodium, Na+ |
| Lilac | Potassium, K+ |
| Brick red | Calcium, Ca2+ |
| Apple green | Barium, Ba2+ |
| Flame colour | Red |
|---|---|
| Ion present | Lithium, Li+ |
| Flame colour | Yellow-orange |
|---|---|
| Ion present | Sodium, Na+ |
| Flame colour | Lilac |
|---|---|
| Ion present | Potassium, K+ |
| Flame colour | Brick red |
|---|---|
| Ion present | Calcium, Ca2+ |
| Flame colour | Apple green |
|---|---|
| Ion present | Barium, Ba2+ |