6.1 Electrolysis
1 2
H
What are the missing values?
Use the table.
Li Be
Na Mg
3
4 5
13 April 2015
6 7 0
He
B C N O F Ne
Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Symbol
Outer
electrons
Ion
Charge
Li
N
5
Cl
Ca
K
Al
O
1
6
+1
-2
Br
Na Ne
Remember: Ions are charged atoms. 8 is the magic number of electrons in the
second and third shells.
6.1 Electrolysis
13 April 2015
Key words
Electrolysis
electrolyte
ions
Anode
cathode
inert
• Ionic compounds can undergo electrolysis.
• Which substances can be electrolysed?
• The products of electrolysis.
Electroplating uses
electricity to cover objects
in metal. This can be any
metal but is normally
copper, silver or gold.
Ionic compounds
• Ionic compounds are
made from charged ions
e.g. Sodium Chloride.
Na+ ClThe ions can move in solution or when
the substance is melted (molten).
Electrolysis of Copper Sulfate
-
+
Cu2+
SO4
Anode
Cathode
• Copper sulfate
is an ionic
substance.
Copper forms
positive ions,
sulfate forms
negative ions.
Opposites
attract.
What charge does the sulfate have?
Electrolysis of copper chloride
Write the captions for every
slide to explain what is
happening.
Negative
–
+
Positive
One electrode is negative, the other is positive.
Cathode
–
+
Anode
The negative electrode is called the cathode,
the positive electrode is called the anode.
–
+
Copper chloride
Copper chloride is added to the electrolytic cell.
–
+
CuCl2
Copper chloride has the formula CuCl2.
Cathode
–
+
Anode
Copper
chloride
solution
CuCl2
Copper chloride solution is bright blue in colour.
Cathode
–
+
Anode
Cl
Cu2+
Cl
It is made of a copper ion with a 2+ charge, and two chlorine
ions with a charge of 1– on each.
Cathode
–
Cu
+
Anode
Cl
Cl
The copper ion is attracted to the cathode, where it gains two
electrons and becomes a copper atom.
Cathode
–
+
Cu
Cl
Anode
Cl
The chlorine ions are attracted to the anode, where they lose an electron
each and become chlorine atoms and then chlorine molecules.
The products of electrolysis
• What is produced on the electrodes?
– Metal forms on the cathode (-)
– Sulfate forms on the anode (+)
13 April 2015
6.1 Electrolysis
• Electrolysis involves splitting up a substance
using electricity.
• Ionic substances can be electrolysed when
they are molten or in solution.
• In electrolysis positive ions move to the
negative electrode (cathode) and negative
ions move to the positive electrode (anode).
Key words
Electrolysis
electrolyte
ions
Anode
cathode
inert