Presentation on theme: "Many ionic compounds are coloured. The colour of the compound is caused by the metal ion which is present in the compound. It is usually a transition."— Presentation transcript:
Many ionic compounds are coloured. The colour of the compound is caused by the metal ion which is present in the compound. It is usually a transition metal ion which gives the colour to ionic compounds.
CompoundColour Ion responsible for colour copper(II) sulphate or copper(II) nitrate. Blue Copper(II) or Cu 2+ Nickel(II) sulphate or nickel(II) chloride GreenNickel(II) or Ni 2+ Sodium chromate or potassium chromate Yellow Chromate or CrO 4 2-
Migration of Ions Being able to watch ions move depends on two facts: ions have electrical charges and many ions have characteristic colours These allow us to observe the movement, or migration, of ions when we apply an electric current to an ionic solution.
A DC power supply connected to copper(II) dichromate solution. Orange negative dichromate ions (Cr 2 O 7 2- ) attracted to positive electrode Green copper (II) dichromate solution Blue positive coppers ions (Cu2 + ) attracted to positive electrode