Cations and anions
Cations are positively (+) charged ions while anions are negatively (−) charged. This can be remembered with the help of the following mnemonics.
- Cats have paws ⇔ Cations are pawsitive.[5]
- Ca+ion: The letter t in cation looks like a + (plus) sign.[6]
- An anion is a negative ion. (An
egativeion ⇒ Anion).[7]
Cation vs. anion: positive vs. negative
The t in cation looks like a plus sign: "ca+ion".
Cation is positive, anion is negative.[8]
Redox reactions
A redox reaction is a chemical reaction in which there is a change in oxidation state of atoms participating in the reaction.
Ions
An atom (or ion) whose oxidation number increases in a redox reaction is said to be oxidized (and is called a reducing agent). It is accomplished by loss of one or more electrons. The atom whose oxidation number decreases gains (receives) one or more electrons and is said to be reduced. This relation can be remembered by the following mnemonics.
- Leo says Ger! or Leo the lion, Ger! can be used to represent Loss of electron is oxidation; Gain of electron is reduction.[9][10]
- Oil Rig: Oxidation is loss; Reduction is gain (of electrons).[11]
Electrodes
An electrode in which oxidation takes place is called an anode while in that which reduction takes place is called cathode. This applies for both electrolytic and electrochemical cells, though the charge on them reverses. The red cat and an ox mnemonics are useful to remember the same.
- Red cat: Reduction at cathode
- An ox: Anode for oxidation.[12]
- The words oxidation and anode, both begin with vowels.
- Also, both reduction and cathode begin with consonants.[7]
- Fat Cat: electrons flow From Anode To Cathode
