electrolysis

• a solid ionic compound can't be electrolysed because the ions are fixed in place and can't move.
• molten ionic compounds can be electrolysed, because the ions are free to move.
• positive metal ions/cations are reduced [gain electrons] to atoms at the cathode. negative ions are oxidised to atoms as the anode.
• in aqueous solutions, there will be the ions from the ionic compound and hydrogen ions + hydroxide ions.
• at the cathode, if H+ ions and metal ions are present, hydrogen gas will be produced if the metal is more reactive than hydrogen. [sodium, potassium, lithium, iron, chromium, nickel, tin, lead]
• at the anode, if halide ions are present, molecules of halides will be formed. if no halide ions are present, then oxygen will be formed from the hydroxide ions.