Anions vs Cations

Specification Point 1.57C (Paper 2C Only):

Know that Anion and Cation are terms used to refer to negative and positive ions respectively

ANION: Non-metals as they are negative ions and will be attracted to the positive electrode.

Reaction at the Positive Electrode (Anode)

• Anions (Negative ions) are attracted to the positive electrode.
• When they get to the electrode, they lose electrons so that they form atoms.

Example: When Lead (II) Bromide is electrolysed, Bromide ions lose an electron to form bromine atoms:

2Br ^–     –     2e^–     →     Br₂

*Bromine is formed at the anode

CATION: Metals are positive ions and will be attracted to the negative electrode

Reaction at the Negative Electrode (Cathode)

• Cations (Positive ions) are attracted to the negative electrode.
• When they get to the electrode, they gain electrons so that they are converted into their atoms.

Example: When Lead (II) Bromide is electrolysed, Lead (II) Ions gain electrons to form Lead Atoms:

Pb²⁺     +     2e^–     →     Pb

*Lead is formed at the cathode